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1.
Twenty 4-month-old calves were infected with O ostertagi and/or T axei and the responses to phytolectins were evaluated. Whole blood cultures were incubated with phytohemagglutinin (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM). The blastogenic response was determined by tritiated thymidine uptake with results presented as counts per minute (cpm), stimulation indices (SI) and a mononuclear cell responsive index determined by dividing the phytomitogen induced cpm by the absolute mononuclear cell number per ul. The control group results were adjusted to 100 percent and changes in the percentage difference by the parasitized calves was determined. There was a decline in lymphocyte responsiveness to PHA beginning at the time of infection. Significant depression of responses to PHA was observed in all parasitized calves 8 weeks after infection although clinical signs of parasitism did not occur. Lymphocyte responses to PW, were not different in infected calves from the control, although the O ostertagi group had significantly higher PWM mean upon than the calves infected with T. axei. A slight depression in response to Con A was also observed at 8 weeks after infection followed by a significant increase after 10 weeks. The immunosuppression appeared to be a feature of gastrointestinal parasitism and related to infections with O. ostertagi and/or T. axei.  相似文献   

2.
In vivo inoculation of three-month-old calves with sodium diethyldithiocarbamate (DTC), killed Corynebacterium parvum or mycobacterium cell wall extract (MCWE) resulted in an enhancement of in vitro peripheral blood lymphocyte blastogenic responses to mitogens phytohemagglutinin (PHA) and Concanavalin A (Con A) in the first three days after treatment. In a separate experiment, blood lymphocytes isolated from a healthy nontreated calf were incubated in vitro in presence of each of the same immunostimulating agents and tested for their blastogenic responses to PHA and Con A. The results showed that all immunostimulants, excepting DTC, enhanced the in vitro blastogenic responses of lymphocytes to PHA and Con A. Finally, addition of MCWE to cultures of blood lymphocytes isolated from calves vaccinated intramuscularly with bovine rotavirus and adjuvant resulted in an enhancement of the in vitro lymphocyte transformation to rotavirus. Our study demonstrated that DTC, killed Corynebacterium parvum and mycobacterium cell wall extract were able to enhance bovine T cell proliferation in vitro.  相似文献   

3.
The ability of lymphocytes from newborn calves to undergo blastogenic responses to the mitogens Concanavalin A (Con A), phytohemagglutinin (PHA), or Pokeweed Mitogen (PWM), and immunomodulation of these responses by neonatal calf serum was assessed as a function of age. Lymphocytes were obtained from thymus, spleen, and mesenteric lymph nodes of 1-, 2- to 3-, 5- to 7-, and 9- to 10-d-old calves, aliquoted and incubated (+/- mitogens) in sera from 1-, 2-, 3-, or 7- to 10-d-old calves. Lymph-node lymphocytes responded least when cultured in sera from 1-d-old calves, regardless of mitogen or age of cell donor; the response increased as age of serum donor increased (P less than .05). Splenic lymphocytes responded similarly (P less than .005). However, when cultured in sera from older calves, splenic lymphocytes from older calves responded greater to PWM than did those from younger calves. Thymic lymphocytes responded minimally to PWM and PHA. Their response to Con A increased (P less than .005) with age of serum donor calf, but the effect was greatest on lymphocytes from 5- to 7-d-old calves. Mixing experiments with varying ratios of 1-d-old calf serum: 10-d-old calf serum suggested that serum from 1-d-old calves contained suppressive activity. Serum cortisol level (measured by radioimmunoassay) was 30 +/- 4.6 ng/ml in calves at 6 h of age and declined to 5.5 +/- 1.1 ng/ml by 10 d. Charcoal treatment to remove steroids did not enhance blastogenesis. Addition of cortisol (50 ng/ml) to charcoal-treated sera resulted in inhibition of response to PHA, but no change in response to Con A or PWM. Further investigation is indicated to characterize this immunosuppressive activity and to establish its relationship to disease susceptibility.  相似文献   

4.
Possible immunomodulation by low-level infection with Ostertagia ostertagi was studied in 4-month-old calves. Six groups of 4 calves each were subjected to the following regimens: group 1--nonparasitized controls; group 2--nonparasitized, but challenge exposed at day 64 with Brucella abortus strain 19 vaccine (BA) and at day 78 with IV administration of a soluble third-stage larval (L3) antigen preparation of O ostertagi (OAG); group 3--nonparasitized, but challenge exposed at day 78 with 75 x 10(3) L3 of O ostertagi; group 4--continuously parasitized by weekly dosing with 30 x 10(3) L3 of O ostertagi; group 5--continuously parasitized by weekly dosing with 30 x 10(3) L3 of O ostertagi, then challenge exposed on day 64 with BA and on day 78 with IV inoculation of OAG; and group 6--continuously parasitized by weekly dosing with 30 x 10(3) L3 of O ostertagi, then challenge exposed on day 78 with 75 x 10(3) L3 of O ostertagi. Over the initial 10 weeks of the study, nonparasitized calves, (groups 1, 2, and 3) had higher body weight, blood lymphocyte (BL) response to phytohemagglutinin (PHA), and significantly (P less than 0.05) higher feed consumption and lymphocyte numbers, whereas parasitized calves (groups 4, 5, and 6) had higher BL responses to pokeweed mitogen (PWM) and significantly (P less than 0.05) higher neutrophil and eosinophil numbers, plasma pepsinogen (PP) values, and BL response to OAG.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

5.
Twelve calves were raised helminth-free until 9 weeks of age when six were orally inoculated with 100,000 Ostertagia ostertagi infective stage larvae (L3). Three uninfected and three experimentally infected calves received intradermal injections of sterile saline and soluble larval extract (SLE) from O. ostertagi L3 with a protein concentration ranging from 1 to 200 micrograms ml-1. Biopsies were performed 48 h post-injection. A kinetic study was performed on the remaining six calves, three infected and three uninfected, using a 100 micrograms ml-1 concentration of SLE and taking biopsies 1, 4, 8, 12, 24, and 72 h post-injection at both the saline and SLE-injected sites. All calves had an immediate wheal and increase in skin thickness at the SLE-injected sites. The numbers of eosinophils infiltrating SLE-injected sites as compared to saline-injected sites were significant in both uninfected and infected calves, but the infected calves had significant numbers to a wider range of SLE concentrations and had significantly higher numbers than uninfected calves in the kinetic study. Infected calves also had significant numbers of basophils in the dose response study at concentrations of 5 and 100 micrograms ml-1 SLE. Neutrophil infiltration was similar in both groups and was significant at SLE-injected sites early in the kinetic study. Detectable mast cells were decreased in SLE-injected sites of infected animals and perivascular accumulation of mononuclear and some polymorphonuclear cells was observed in the deep dermis of infected animals.  相似文献   

6.
The possible development of type-1 hypersensitivity reactions in the abomasal mucosa caused by soluble L3 products of Ostertagia ostertagi was studied in 4-month-old calves sensitized by repeated exposure to L3 over a 50-day period followed by anthelmintic treatment. Four groups each of 4 calves were used. Group 1 served as nonsensitized controls and group 2 as sensitized controls, group 3 was challenge exposed at 2-week intervals beginning at week 10 with a soluble L3 product (OAG), and group 4 was challenge exposed at 2-week intervals with an oral dose of L3, followed by anthelmintic treatment 3 days later. All calves infected with L3 became sensitized, as indicated by a positive reaction to an intradermal skin test. However, a passive cutaneous anaphylaxis was only partly effective in indicating the presence of homocytotropic antibody in the infected calves. Sensitized calves had significantly (P less than 0.05) higher eosinophil counts and plasma pepsinogen values for the entire 14 weeks than uninfected controls. Globule leukocyte and mast cell counts from the abomasal mucosa were also significantly (P less than 0.05) higher. Studies for possible immunomodulation revealed that lymphocyte counts decreased between every 2-week challenge-exposure period for groups-3 and -4 calves. A transient depression of blood lymphocyte (BL) responses to phytohemagglutinin (PHA), a T-cell mitogen, was observed over the first 8 weeks in the infected calves. Increases in BL responses to OAG were also observed. Differences were not observed in BL responses to pokeweed mitogen, a T- and B-cell mitogen. Blood lymphocyte responses to PHA in group-3 calves were low following the initial challenge exposure with OAG.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

7.
Postnatal changes in lymphocyte function of dairy calves   总被引：1，自引：0，他引：1  
Lymphocyte blastogenic response, B-lymphocyte population and antibody-producing activity of lymphocytes were determined to evaluate the lymphocyte function in neonatal calves during the first 4 weeks of life. The mean percentage of B-lymphocytes ranged from 10.2 to 12.5% during the first 14 days of life and from 15.3 to 17.5% in calves from the day 21 to day 28 after birth. The absolute number of B-lymphocytes increased significantly (P less than 0.05) from 370/microliters at birth to 736/microliters on day 28 after birth. The mean stimulation index of blastogenic response, measured by fluorometric assay, ranged from 5.75 to 6.61 with Con A, from 5.29 to 5.98 with PHA and from 1.89 to 2.50 with PWM. The mean (+/- S.D.) number of plaque forming cells ranged from 22.0 (+/- 12.0) to 24.7 (+/- 9.2) in cultured lymphocytes from 5 calves at birth to 14 days after birth and their levels increased markedly from 137.8 (+/- 88.3) to 162.0 (+/- 57.8) in lymphocytes from 20 days to 28 days after birth. The present study showed that antibody-producing activity of lymphocytes is lower in calves within 3 weeks after birth compared to that of calves 3 weeks after birth, indicating that neonatal calf lymphocytes have a low antibody-producing activity at least up to 1 month after birth.  相似文献   

8.
A fluorometric assay was applied to evaluate blastogenesis of equine lymphocytes. Optimal culture conditions were as follows; concentrations of phytohaemagglutinin-P (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM) were 1 microgram/ml, 40 micrograms/ml and 10 micrograms/ml, respectively, when 5 X 10(5) lymphocytes were incubated with culture medium containing 20% pooled horse serum (PHS) for 120 hours. The relative mean stimulation index of healthy non-pregnant mares were 5.107 +/- 0.323 (M +/- SE) with PHA, 4.019 +/- 0.183 with Con A and 3.610 +/- 0.131 with PWM. Sequentially the blastogenic responses of lymphocytes from twenty mares were observed during various stages of the perinatal period. Response decreased gradually before parturition was lowest at the time of parturition (PHA: 1.923 +/- 0.174, Con A: 1.698 +/- 0.206 and PWM: 1.706 +/- 0.177), and then increased gradually after parturition towards non-pregnant levels.  相似文献   

9.
The in vivo and in vitro effects of Trichinella spiralis excretory-secretory (ES) antigens on porcine peripheral blood lymphocyte (PBL) responses induced with mitogens (phytohemagglutinin, PHA; concanavalin A, Con A; pokeweed mitogen, PWM) or unrelated antigen (Protein A) were studied to determine whether ES antigens depress lymphocyte responses in experimental swine trichinosis, and/or if this response was manifested after lymphocytes from infected pigs had been pretreated with ES antigens. Additionally, the range of inhibition of lymphocyte responses was tested in parasite-free pigs using different doses of ES antigens and compared with the responsiveness of control cultures from the same animals. The responses of lymphocytes from pigs inoculated with 4 x 10(3) muscle larvae (ML) were strongly depressed (P < 0.05) at post-inoculation days (PID) 7 (after stimulation with PHA), 14, 35 (Con A or PWM), and 49 (PWM). At PID 56 and 63 the lymphocytes from T. spiralis-infected pigs responded better (P < 0.05) to all three mitogens than those from non-infected controls. After 7 weeks post-inoculation, PBL which were pretreated with 10 or 250 micrograms ml-1 of ES antigens showed significantly weaker (P < 0.05, P < 0.001) responses to PWM or PHA, respectively, than those from non-infected animals. The responsiveness of lymphocytes from both groups of pigs to Protein A was not affected by the pretreatment with ES antigens in vitro. The responses of lymphocytes from the parasite-free pigs induced by PHA, PWM or Protein A were strongly depressed (P < 0.01) after in vitro pretreatment regardless of the dose of ES antigens (5, 10, 15, or 20 micrograms ml-1) applied.  相似文献   

10.
Immune responses and lymphoreticular morphology were studied in 3 groups of yearling Hereford steers fed hypoalimentative, maintenance and hyperalimentative diets for 142 days. Significant decreases in plasma protein levels and circulating lymphocyte levels occurred in low energy intake steers. Percent circulating lymphocytes bearing surface immunoglobulins and serum levels of IgG and IgM did not vary significantly within or between groups. Antibody responses to Brucella abortus bacterin inoculated on day 63 were similar in all 3 groups. Antibody responses to chicken erythrocytes inoculated on day 88 were significantly lower in hypoalimentated steers. Differences between groups in lymphocyte blastogenic responses to phytohemagglutinin (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM) were not significant. Hyperalimentated steers had significantly depressed PWM responses compared to a baseline value established for that group. In addition, hypoalimentated steers tended to have elevated responses to PHA, although differences were not significant. There were no significant differences between groups in dermal hypersensitivity responses to tuberculin following sensitization with viable Bacillus Calmette-Guerin (BCG). The thymuses of hypoalimentated steers were markedly atrophied but lymph nodes and splenic white pulp were normal. Thymus, lymph nodes and spleen were normal in hyperalimentated steers.  相似文献   

11.
Four groups of 18 beef calves each were used to evaluate effects of different treatments on parasite control and weight gains. The investigation extended from November 1986 (weaning) to October 1987. Group-1 calves were treated with ivermectin (200 micrograms/kg of body weight, SC) at approximately 6-week intervals for a total of 8 treatments; group-2 calves were given the same dosage of ivermectin by the same route of administration as group-1 calves in November, March, and July; group-3 calves were given fenbendazole paste (5 mg/kg, PO) at the same times as group-2 calves; and group-4 calves served as untreated controls with provision for ivermectin salvage treatment. All groups grazed on individual pairs of larval-contaminated, 1.6-ha pastures. Highest (P less than 0.05) initial worm counts in fall tracer calves were found in group 3 (Ostertagia ostertagi and Trichostrongylus axei adults) and group 4 (O ostertagi and Haemonchus adults). Fecal egg counts of group-1 calves were low throughout the experiment and pasture larval counts remained negligible after July. Egg counts and larval counts of other groups remained higher into summer. Worm counts, including O ostertagi inhibited early fourth-stage larvae (EL4), were highest (P less than 0.05) in groups-3 and -4 spring tracer calves; numbers of O ostertagi EL4 were similarly high in groups 2, 3, and 4; and T axei counts were highest (P less than 0.05) in groups-3 and -4 yearlings slaughtered in spring. Liveweights of group-1 calves were greater (P less than 0.05) than in other groups from March 2 to October, and by July 2, group-2 calves had a liveweight advantage over group-4 calves. Group-3 calves had the lowest rate of gain from March to July and mean liveweight of the group was less (P less than 0.05) than in all other groups from April to October. Only minimal worm numbers were recovered from groups-1 or -2 calves in October. Large numbers of O ostertagi and T axei were recovered from group-4 calves and O ostertagi from group-3 calves. A few calves in groups 3 and 4, but particularly in group 4, were affected by type-II disease (chronic to acute gastritis caused by maturation and emergence of previously inhibited larvae) from August to October. Final mean liveweights in descending order were 365 kg in group 1, 328 kg in group 2, 316 kg in group 4, and 281 kg in group 3.  相似文献   

12.
Immune modulation by Ostertagia ostertagi and the effects of diet   总被引：1，自引：0，他引：1  
IgG1 antibody responses to Ostertagia ostertagi third stage larvae (L3) and the third party antigen, keyhole limpet haemocyanin (KLH), and faecal egg counts were determined in calves infected with a single dose of O. ostertagi and in uninfected, pair-fed calves. The infected and uninfected calves were given diets either high (H) or low (L) in protein and energy. The diets were within the normal range of husbandry practice in the UK. IgG1 antibody responses to L3 antigen were significantly greater from 6 weeks post-infection in infected calves given the L diet than in infected calves given the H diet (P less than 0.05). The effects of diet and infection on anti-KLH IgG1 responses were independent of each other. IgG1 responses to KLH were decreased by infection and by the L diet compared with the H diet.  相似文献   

13.
Nutritional and physiologic effects of clinically apparent and subclinical Ostertagia ostertagi infections were studied in 3 groups of 5 calves each. Group-1 calves were inoculated with 100,000 Ostertagia ostertagi third-stage larvae (L3)/calf/wk for 14 weeks. Group-2 calves were inoculated with 10,000 L3/calf/wk for 14 weeks, and group-3 calves were no inoculated. Calves in group 1 had decreased dry matter intake and feed utilization from 4 weeks after initial inoculation. Group-2 calves had no changes in dry matter intake, but had decreased feed utilization at 12 and 14 weeks. Calves with clinically apparent infections (group 1) lost a mean weight of 11.8 kg, whereas calves with suclinical infections (group 2) lost a mean of 46.6 kg, and control calves lost a mean of 60.7 kg. Calves with O ostertagi infections (group 1 and 2) also had decreased carcass quality at slaughtering, which was reflected in decreased dressing weights and increased water-holding capacity of the rib-eye muscle. Calves in groups 1 and 2 also had lower carcass yield and rib-eye muscle weight, and group-1 calves had decreased protein content. Results of hematologic, pathologic, parasitologic, and clinical examinations mirrored nutritional changes.  相似文献   

14.
The residual effect of treatment with ivermectin after experimental reinfection in calves was tested. Twenty-four calves were divided into 6 groups of 4 calves each. All calves received a primary infection of 50,000 larvae of both Ostertagia ostertagi and Cooperia oncophora and 1000 Dictyocaulus viviparus larvae. Calves of group 1 remained untreated, and all other calves were treated 21 days after primary infection (0.2 mg/kg injected subcutaneously). Calves of groups 1 and 2 were slaughtered 7 days later. Calves of groups 3-6 were reinfected with the same number of larvae 3 days, 1, 3 and 6 weeks after treatment respectively. Slaughter was 21 days after reinfection. Based on post-mortem worm counts the efficacy of ivermectin after primary infection was 99.7% for O. ostertagi, 95.1% for C. oncophora and 100% for D. viviparus. A residual effect was present for at least one week, but could not be observed 3 weeks after treatment.  相似文献   

15.
In the present study peripheral blod mononuclear cells (MNC) obtained from normal uninfected lambs were used to study the possible effects of bovine respiratory syncytial virus (BRSV) on lymphocyte responses to the mitogens, phytohaemagglutinin (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM) in vitro. Live BRSV had a depressive effect on the proliferative responses of normal MNC to PHA, Con A and PWM. Inactivated BRSV and a commercial preparation of prostaglandin E2 were also found to depress the proliferative responses of normal ovine MNC to PHA but recombinant tumour necrosis factor-alpha (TNF-alpha) had no such effect. Serum samples obtained from BRSV-infected lambs contained substances inhibitory to PHA-driven lymphocyte blastogenesis. Memory blastogenic responses to border disease virus (BDV) of lymyphocytes obtained from lambs previously primed with BDV were significantly reduced when lymphocytes were exposed to infectious BRSV.  相似文献   

16.
A blind-well chemotaxis chamber method was used to indicate migration stimulation of bovine neutrophil and eosinophil polymorphonuclear leukocytes and macrophages as related to ostertagiasis. Live exsheathed Ostertagia ostertagi 3rd-stage larvae (L3) and soluble L3 antigen (SLA), prepared by freeze thawing and sonic disruption of L3, enhanced cellular migration for eosinophils, but not for neutrophils and macrophages. Products of lymphocytes cultured with SLA for 3 to 6 hours were also examined, using lymphocytes from peripheral blood of helminth-free cattle and cattle infected with O ostertagi or Trichostrongylus axei. Lymphokines that enhanced cellular migration of neutrophils, eosinophils, and macrophages were present in culture supernatants of SLA-stimulated lymphocytes from O ostertagi-infected cattle, but not from cattle infected with T axei or helminth-free cattle. Seemingly, L3 and SLA were stimulants of eosinophil migration. Further, neutrophil, eosinophil, and macrophage migration was modulated by lymphokines produced by SLA-stimulated lymphocytes from cattle with ostertagiasis.  相似文献   

17.
Ten parasite-free lambs were drenched with oxfendazole on days 0 and 28 and, one day after each drench, were injected with human erythrocytes and ovalbumin. Ten other antigen-injected lambs were not drenched (controls). Lymphocytes collected 3 days after each antigen injection and cultured in RPMI 1640 plus 5% fetal calf serum (FCS) and lymphocytes collected 3 days after the first and 3 and 7 days after the second antigen injection and cultured in 50% autologous serum had decreased blastogenic activity compared with control lymphocytes. After the second drench, decreased blastogenesis was seen with lymphocytes collected on days 3 and 7 and cultured in 5% FCS and concanavalin A (Con A) and on day 3 when cultured in 5% FCS and phytohaemagglutinin (PHA). Decreased blastogenesis was also seen with lymphocytes collected 7 and 29 days after the second injection of antigen and cultured in 50% autologous serum plus Con A and on days 3, 7 and 29 when cultured in 50% autologous serum and PHA.Significantly depressed antibody responses to both antigens were seen after the second drench. The serum complement level was depressed 3 days after the second injection of antigen. Serum nitric oxide levels were significantly depressed 3 and 21 days after the first and 7 and 21 days after the second injection of antigen. There were no differences in levels of growth-promoting hormones but the drenched lambs gained significantly more weight than the controls.Abbreviations C complement - Con A concanavalin A - cpm counts per minute - EIA enzyme immunoassay - FCS fetal calf serum - IGF insulin-like growth factor - oIGF-1 ovine insulin-like growth factor-1 - PBS phosphate-buffered saline - PHA phytohaemagglutinin  相似文献   

18.
Daily changes in serum gastrin and pepsinogen concentration have been studied during two types of infection with Ostertagia ostertagi in calves. In a first experiment two calves were trickle infected (10 times 10,000 L3 Ostertagia) and two animals received a single infection of 100,000 L3 Ostertagia. Gastrin and pepsinogen changes are discussed in relation to adult wormburdens. The second experiment involved 8 calves and was designed to investigate pepsinogen and gastrin changes following a challenge infection in previously sensitized calves. The high dosed group was infected with 5,000 L3 O. ostertagi during 30 days, the low dosed group received 500 L3 O. ostertagi and group 3 served as uninfected control. At day 41 post infection all animals were treated with oxfendazole and on day 61 challenged with 100,000 L3 O. ostertagi. Only in the high dosed group a distinct pepsinogen and gastrin reaction was noticed. Both parameters dropped to almost preinfection levels after treatment. Two days post challenge a moderate rise (+/- 1,000 mU tyr) of the pepsinogen concentration was observed in the previously infected animals and gastrin showed a temporary slight increase in several animals 8 to 10 days post challenge. The effect of treatment and challenge infection is discussed in relation to gastrin and pepsinogen changes and immunity.  相似文献   

19.
The influence of colostral leukocytes on lymphocyte counts in the blood of calves and on lymphocyte responses, in particular the Concanavalin A-induced blastogenic response in vitro and the formation of antibodies against sheep erythrocytes, was investigated for four weeks postnatum using four experimental groups. The calves received either complete colostrum (COL+, n = 16), cell-depleted colostrum (COL-, n = 16), colostral cell-supplemented milk substitute (MS+, n = 7) or pure milk substitute (MS-, n = 6) during their first three days of life. In contrast to the calves fed with cell-depleted colostrum (COL-) the calves fed with complete colostrum (COL+) showed no decrease of lymphocyte numbers in the blood on the second day of life, uniform blastogenic responses to two different Concanavalin A concentrations, slightly enhanced antibody formation against sheep erythrocytes and a high spontaneous proliferation of mononuclear cells during the first week of life. In the calves fed with milk-substitute supplemented with colostral cells (MS+) a higher blastogenic response to Concanavalin A and an intensified formation of antibodies against sheep erythrocytes was observed as compared to the MS- calves. A passage of vital colostral lymphocytes through the intestinal wall is postulated. They seem to stimulate and regulate the blastogenic response and enhance the T-helper cell-dependent formation of antibodies against sheep erythrocytes in calves.  相似文献   

20.
Lymphocyte numbers and activities were evaluated at 2, 4, 8 and 12 weeks of age in two calves with lethal trait A46 (A46), a genetic disorder affecting intestinal zinc absorption. Plasma zinc concentrations declined to subnormal by 3 weeks of age, after which anorexia, diarrhea, alopecia and hyperkeratosis occurred. Lymphocyte response to phytohemagglutinin-P (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM) stimulation was variably reduced. CD4+ T-lymphocytes were subnormal on at least one observation period following onset of zinc deficiency, and relative numbers of B lymphocytes were decreased at 8 weeks. Secondary antibody responses to bacteriophage phi X 174 were significantly reduced. The results demonstrate that calves homozygous for the A46 trait have normal numbers of functional lymphocyte subpopulations at birth, and that the activity of their lymphocytes is altered once the calves become zinc deficient.  相似文献   

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