Lymphocyte functions in cattle affected with leukocyte adhesion deficiency (LAD, termed BLAD in cattle) were evaluated by lymphocyte markers, blastogenic response, and immunoglobulin concentrations; mononuclear phagocyte functions were assessed by chemotactic and luminol-dependent chemiluminescent (CL) responses to determine the effects of impaired expression of leukocyte CD18 on mononuclear cell functions. Deficient CD18 expression on lymphocytes and mononuclear phagocytes from cattle with BLAD was clearly detected by use of flow cytometric analysis. There were no significant differences in the population of peanut agglutinin (PNA)-positive and surface immunoglobulin-bearing blood lymphocytes from clinically normal cattle and cattle with BLAD, as determined by flow cytometric analysis. Lymphocytes from cattle with BLAD had strong mitogen-induced blastogenic responses, which were greater than those from controls. Adherence of mononuclear phagocytes from cattle with BLAD was markedly impaired, and their chemotactic responses had diminished values, compared with those of controls. Luminol-dependent CL of mononuclear phagocytes from affected cattle, stimulated by opsonized zymosan, had significantly (P < 0.01) decreased values, compared with those of controls. Concentrations of IgG were markedly increased in serum from cattle with BLAD, compared with those in controls. These results indicated that impaired expression of leukocyte CD18 has marked effects on adhering activity of mononuclear phagocytes, and significantly inhibits CL response of mononuclear phagocytes mediated by inactivated-complement 3b-dependent functions. High selective immunoglobulin concentrations indicated that lymphocytes of B-cell lineage may have normal function.

Eighteen female lambs with prior exposure to Haemonchus contortus infections were ovariectomized and assigned to 1 of 3 replacement regimens: 0, 25, or 250 mg of progesterone/d delivered IM. After 3 weeks of hormonal treatment, all lambs were inoculated with 100,000 infective larvae of H. contortus. After 8 weeks of hormonal treatment, a blastogenic assay was performed on blood lymphocyte populations, and the abomasum from each lamb was obtained for larval and adult worm recoveries of H. contortus. Lambs of the 25 mg of progesterone group had significantly (P < 0.05) reduced blastogenic response to concanavalin A and greater adult and larval populations, compared with controls. Lambs of the 250 mg of progesterone group had worm burdens and lymphocyte blastogenesis values intermediate between those of the other treatment groups.

Newly hatched chickens were treated with the trichothecene mycotoxin, T-2 toxin, during the first day of life. Control chickens were treated with other agents known to cause immunosuppression-cyclosporine, cyclophosphamide, and aflatoxin. Chickens were infected on day 6 (5 days after treatment with T-2 toxin) by intraperitoneal inoculation with Salmonella typhimurium. Blood samples were collected from treated chickens (noninfected) and used to assess the responsiveness of blood lymphocytes to T-cell or B-cell mitogens, phytohemagglutinin, or lipopolysaccharide, respectively. The T-2 toxin had a profound negative effect on the ability of the chickens to resist salmonellosis, as measured by survival. However, the toxin effect in reducing phytohemagglutinin- and lipopolysaccharide-stimulated mitogenesis, though significant (P > 0.05), was not severe. Our data indicate a direct effect of T-2 toxin on native resistance to systemic salmonellosis, which was not accompanied by marked alteration in T- or B-cell responses to mitogenic stimulation.

In this study, the immune responses to and protective efficacy of a live attenuated Salmonella-delivered vaccine candidate secreting the papA, papG, iutA, and clpG antigens of Escherichia coli were evaluated against infection with avian pathogenic E. coli (APEC) in layer chickens. Primary vaccination was done at age 7 d and booster vaccination at age 5 wk. The levels of intestinal secretory immunoglobulin A specific to the 4 antigens were significantly higher in the vaccinated group than in the control group. A potent lymphocyte-proliferation response and increased levels of interferon-γ, interleukin-2, and interleukin-6 in the plasma and in culture supernatants of antigen-stimulated lymphocytes from the vaccinated group suggested significant induction of the cell-mediated immune response in this group compared with the control group. Upon challenge with a virulent APEC strain at 8 wk of age, the vaccinated group had no deaths, whereas the control group had a 15% mortality rate. In addition, the morbidity rate was significantly higher in the control group (55%) than in the vaccinated group (15%). Thus, giving primary and booster vaccination with the Salmonella-delivered APEC vaccine candidate significantly elevated both mucosal and cellular immune responses, which protected the chickens against colibacillosis.

The present study investigated the effects of vaccinating sows and piglets or piglets alone against Haemophilus parasuis on the prevalence of H. parasuis in nasal swabs, on the humoral and cellular immune responses, and on the production parameters of piglets at 3 Korean farms with a clinical history of polyserositis caused by H. parasuis. Piglets born to vaccinated or non-vaccinated sows were subdivided into 3 groups: vaccinated sows and vaccinated pigs (VS-VP), non-vaccinated sows and vaccinated pigs (NVS-VP), and non-vaccinated sows and non-vaccinated pigs (NVS-NVP). The proportion of piglets with positive nasal swabs was significantly lower (P < 0.05) in the vaccinated animals (VS-VP and NVS-VP groups) than in the non-vaccinated animals (NVS-NVP group) at 35 and 60 d of age at the 3 farms. The overall growth performance (from 7 to 60 d of age) of the vaccinated piglets was significantly better (P < 0.05) than that of the non-vaccinated piglets at the 3 farms. Piglets in the VS-VP group had significantly higher levels (P < 0.05) of H. parasuis-specific IgG antibodies, lymphocyte proliferation, and interferon-γ-secreting cells than piglets in the NVS-VP and NVS-NVP groups on days 1, 7, 21, 35, and 60 after birth at the 3 farms.

Objective—To determine effects of infection with bovine leukosis virus (BLV) on lymphocyte proliferation and apoptosis in dairy cattle. Animals—27 adult Holstein cows. Procedures—Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood from lactating Holstein cows seronegative for BLV (n = 9 cows), seropositive for BLV and aleukemic (aleukemic; 9), and seropositive for BLV and persistently lymphocytotic (PL; 9). Isolated PBMCs were assayed for mitogen-induced proliferation and were analyzed by means of flow cytometry. The PBMCs from a subset of each group were assayed for apoptosis, caspase-9 activity, and expression of selected genes related to apoptosis. Results—PL cows had significantly higher total lymphocyte counts and significantly lower proportions of T-lymphocyte populations than did BLV-negative and aleukemic cows. Both groups of BLV-infected cows had significantly higher proportions of B cells and major histocompatibility complex II–expressing cells than did BLV-negative cows. Proliferation with concanavalin A was significantly lower for PL cows, compared with proliferation for BLV-negative cows. Pokeweed mitogen–induced proliferation was significantly higher for aleukemic and PL cows than for BLV-negative cows. Gene expression of apoptosis-inhibitory proteins BCL2 and BCL2L1 was significantly higher for aleukemic cows and expression of BCL2 was significantly higher for PL cows than for BLV-negative cows. Conclusions and Clinical Relevance—Cattle infected with BLV had marked changes in PBMC populations accompanied by alterations in proliferation and apoptosis mechanisms. Because the relative distribution and function of lymphocyte populations are critical for immune competence, additional studies are needed to investigate the ability of BLV-infected cattle to respond to infectious challenge.

Cell-mediated immune mechanisms may play a role in the pathogenesis and prevention of pneumonia in cattle caused by Pasteurella haemolytica serotype A1. To determine the circumstances required to stimulate and identify cell-mediated immune responses, calves were vaccinated with a commercial P. haemolytica bacterin or a live commercial P. haemolytica vaccine, or were infected intratracheally with virulent P. haemolytica. All calves were challenge-exposed intratracheally with P. haemolytica 31 d after vaccination or prior infection. Peripheral blood mononuclear cells and mediastinal and superficial cervical lymph node cells were stimulated with antigens prepared from P. haemolytica to evaluate in vitro proliferative responses and gamma-interferon production as measures of cell-mediated immunity. Strong proliferative responses and gamma-interferon production were detected in lymph node cells from calves vaccinated with the live vaccine and from infected calves, especially in response to stimulation with an outer membrane protein preparation from P. haemolytica. Greater proliferative responses and gamma-interferon production were associated with the lymph node nearer the site of bacterin administration (superficial cervical lymph node) or the site of infection (mediastinal lymph node), whereas greater proliferative responses and gamma-interferon production were associated with the more distant lymph node (mediastinal lymph node) in calves vaccinated with the live vaccine. Neither proliferative responses nor gamma-interferon production were detected in peripheral blood mononuclear cells from calves that were vaccinated for or infected with P. haemolytica. Antileukotoxin antibody titers were determined by a serum neutralization assay, and protection against pneumonic lesions was more closely correlated with antileukotoxin antibody responses than with lymphocyte proliferation or gamma-interferon responses.

Lymphocyte stimulation tests (LST), performed using 6 antigen preparations, were compared individually and in pairs. The tests were performed on 433 blood samples collected from elk in Mycobacterium bovis-infected herds. These elk were killed as part of Agriculture and Agri-Food Canada's bovine tuberculosis eradication policy, and mycobacterial culture results were obtained from tissues of each animal The LST, which had the highest total sum of sensitivity and specificity, was a comparative test that used M bovis purified protein derivative (PPD) and M paratuberculosis (johnin) PPD. This test had a sensitivity of 76%, with confidence limits (CL) of 63 to 85% for this estimate, and specificity of 77% (CL, 72 to 81%). The LST, using only M bovis PPD antigen, had a sensitivity of 70% (CL, 57 to 80%) and specificity of 74% (CL, 69 to 79%); when it was compared with culture results, using the kappa statistic, agreement was only 32%. This indicated that the LST identified different elk than did M bovis isolation tests.

Vaccina virus (VV) infection induces specific antibodies and cytotoxic T cells in various animal species. Therefore, helper T cells also should be induced that stimulate the humoral and cellular immune responses. We determined such helper T-cell activity in 2 species after VV infection. Rabbits and rhesus macaques were infected with the Copenhagen strain of VV or with recombinant VV expressing retroviral proteins. Animals of both species developed antibodies and specific proliferative T-cell response. This reactivity could be enhanced by booster infection with VV. The proliferating macaque cells were CD4+ and major histocompatability complex class II-restricted. These data confirm the broad immunogenicity of VV. Expression of additional polypeptides expressed from a recombinant VV does not lead to altered immune response to VV antigens. However, strength of the helper T-cell response, as well as clinical reactions, differed between macaques and rabbits. Infection with recombinant VV as delivery vectors offers the opportunity for combined vaccination against recombinant proteins and does not diminish cellular and humoral immune responses to VV itself.

Cell-mediated immunity was evaluated in intestinal, respiratory, and systemic lymphoid tissues of pigs exposed when 11 days old to virulent transmissible gastroenteritis virus (TGEV), attenuated TGEV, or porcine respiratory coronavirus (PRCV), 3 antigenically related porcine coronaviruses with distinct enteric and respiratory tissue tropisms. Mononuclear cells were prepared from mesenteric lymph nodes (MLN), bronchial lymph nodes (BLN), and spleens of pigs and tested for virus-specific responses by use of lymphocyte proliferation assays. Vigorous MLN and BLN proliferation responses to virulent TGEV and PRCV, respectively, at postinoculation days 8 to 24 were strongly associated with prior detection of TGEV in rectal swab samples and PRCV in nasal swab samples. Gastrointestinal disease and intestinal virus replication, assessed on the basis of rectal virus shedding, were almost exclusively found in the virulent TGEV-inoculated pigs, even though virulent TGEV and a high dose of attenuated TGEV elicited the highest proliferation responses in MLN. Pigs exposed to PRCV or attenuated TGEV did not have clinical signs of disease, and only 1 pig given a high dose of attenuated TGEV shed virus in feces. Porcine respiratory coronavirus replicated in the respiratory tract after either oronasal or aerosol inoculation of virus and induced strong BLN, but not MLN, proliferation responses. A high dose of attenuated TGEV (4 X 10(8) plaque-forming units) was more effective than a lower dose of attenuated TGEV (7 X 10(6) plaque-forming units) in eliciting significant lymphocyte proliferation in MLN and BLN. Cellular immune function, assessed on the basis of mitogen-induced proliferation of lymphocytes, was comparable for all 3 sources of lymphocytes and was not adversely affected by exposure to any of the pigs. The tissue tropism of TGEV and PRCV was associated with induction of virus-specific cell-mediated immune responses, as evidenced by substantial lymphocyte proliferation responses in MLN and BLN, mucosa-associated lymph nodes adjacent to the primary sites of virus replication. The failure of PRCV strain ISU-1 to replicate in the intestinal tract correlated with poor virus-specific cellular immune responses in MLN.