Haemophilus somnus-induced IgE in calves vaccinated with commercial monovalent H. somnus bacterins.

The ability of commercially available Haemophilus somnus bacterins to elicit an immunoglobulin E (IgE) response was examined in healthy calves using enzyme-linked immunosorbent assay (ELISA) and western blotting techniques. Thirty five calves were utilized in this study. Calves in Group 1 (n=7) did not receive any H. somnus vaccination and served as negative controls. Calves in each of Groups 2-5 (n=7 each) were vaccinated on days 0 (primary) and 14 (booster) with one of four commercially available H. somnus bacterins. Sera were harvested on days 0 and 14 and at weekly intervals for a total of 45 days. Sera were tested for the presence of IgE antibodies using a bovine IgE-specific ELISA. Low levels of H. somnus-specific IgE were detected by ELISA in all animals prior to the initiation of the study. All bacterins induced IgE levels that were significantly higher than control levels. Two bacterins elicited higher IgE levels at all time points. Sera were adsorbed against washed whole cells of either Salmonella typhimurium, P. multocida, or H. somnus or extracts of H. somnus. ELISA absorbance values were significantly decreased by adsorption with washed whole cells or extracts of H. somnus, whereas adsorption with other gram-negative bacteria only minimally decreased ELISA absorbance values. These results indicate that commercially available H. somnus bacterins can induce IgE antibody as early as 14 days post-vaccination. This IgE can be detected 45 days after the primary vaccination. Results also indicate that H. somnus-specific IgE antibodies can be found in serum of some cattle, possibly induced by existing or previous sensitization.

Differential serologic response to Mycoplasma ovipneumoniae and Mycoplasma arginini in lambs affected with chronic respiratory disease.

An enzyme-linked immunoabsorbent assay (ELISA) was used to evaluate the levels of antibodies to Mycoplasma ovipneumoniae and M. arginini in lambs with chronic respiratory disease. Sera were obtained from lambs in several flocks at various stages of the clinical disease and tested with sodium dodecyl sulfate (SDS)-treated M. ovipneumoniae and M. arginini whole cells and a crude capsular extract of M. ovipneumoniae as the antigens. There were low levels of antibody to M. ovipneumoniae in flocks sampled at the early stages of infection, whereas increased levels of antibody were present in lambs from flocks that had apparently recovered from the clinical disease. Slowly rising titers of circulating antibodies to M. ovipneumoniae were confirmed by sequential bleeding of lambs during the course of the clinical disease. However, antibody levels of M. arginini were more likely to increase earlier in the disease process. There was significant cross-reactivity between the 2 SDS-treated antigens in both the ELISA test and western immunoblotting. In contrast, the crude capsular extract was specific for detecting antibodies to M. ovipneumoniae.

Synergistic effects of bovine respiratory syncytial virus and non-cytopathic bovine viral diarrhea virus infection on selected bovine alveolar macrophage functions.

The effect of bovine respiratory syncytial virus (BRSV) and non-cytopathic bovine viral diarrhea virus (ncpBVDV) infection on selected bovine alveolar macrophage (AM) functions was investigated. Alveolar macrophages were harvested from 2- to 6-month-old calves seronegative for BRSV and BVDV and inoculated with approximately 1 median cell culture infective dose of virus per AM. Control, BRSV infected, ncpBVDV-infected and BRSV-ncpBVDV coinfected AM cultures were evaluated for Fc receptor expression, phagosome-lysosome fusion, superoxide anion (O2-) production, and chemotactic activity on Days 1, 3, 5, and 7 post-infection. Both single and combined viral infections significantly depressed AM Fc receptor expression, phagosome-lysosome fusion, and secretion of chemotactic factors with a more significant synergistic depression seen in BRSV-ncpBVDV coinfection. Production of O2- by AM was not decreased by either BRSV or ncpBVDV infection, but was significantly decreased by coinfection with BRSV-ncpBVDV. The present study confirms previous reports of BRSV effects on AM functions and indicate that ncpBVDV affects AM functions in vitro. Coinfection with BRSV-ncpBVDV produced a synergistic depression on AM functions.

Occurrence of autoantibodies to cilia in lambs with a 'coughing syndrome'.

A respiratory disease of lambs that has been termed the 'coughing syndrome' has been observed in the mid-western region of the United States of America. Mycoplasma ovipneumoniae (M. ovipneumoniae) and Mycoplasma arginini (M. arginini) were routinely isolated from the respiratory tract of lambs with this disease. A high level of antibodies reactive with ovine cilia of the upper respiratory tract was detected in the sera from many of the lambs in affected flocks but not in sera of lambs from unaffected flocks. The reactivity of these antibodies with cilia was demonstrated by ELISA and confirmed by indirect immunofluorescent staining and western immunoblotting. These antibodies were predominantly of the IgG isotype. They were distinct from cold or warm agglutinins and could be absorbed from the sera with cilia but not with antigens of common bacterial pathogens of the sheep respiratory tract including M. ovipneumoniae, M. arginini, Pasteurella haemolytica, Pasteurella multocida or Neisseria ovis. In addition, their occurrence appeared to be independent of the specific antibodies to M. ovipneumoniae and M. arginini. Western immunoblotting indicated that the antibodies were directed primarily against an antigen with apparent molecular weight of 50 kDa. In one flock from which serial serum samples were collected from the same lambs over a 10-month period, antibodies to ovine cilia developed before the onset of the clinical disease and persisted for a period of several months until most of the lambs had apparently recovered. However, colonization of the respiratory tract of the lambs by M. ovipneumoniae preceded the production of these antibodies. Sequential serum samples taken from another flock, with no known history of this coughing, showed no such antibodies throughout the sampling period. It is suggested that an immunopathologic mechanism involving production of autoantibodies directed against a ciliary antigen of the lambs could be a contributing factor to the pathogenesis of this clinical disease.

Demonstration of a capsule on Mycoplasma ovipneumoniae.

OBJECTIVE: To examine Mycoplasma ovipneumoniae for presence of a capsule and its potential role in adherence. SAMPLE POPULATION: 17 isolates of M ovipneumoniae and 2 isolates of M arginini, recovered from sheep with respiratory tract disease. PROCEDURE: Mycoplasmas were cultured in modified Fills broth medium, ovine fetal lung cells, or ovine tracheal ring explants. Pelleted mycoplasmas or ring cultures infected with mycoplasmas were treated with ruthenium red or polycationic ferritin and visualized by transmission electron microscopy. Reactivity of several lectins with the mycoplasmas was studied by use of a microtitration plate agglutination test. RESULTS: Electron microscopy revealed a large number of M ovipneumoniae cells covered with an electron dense-stained amorphous material suggesting that it was a capsule. Multiple passages of the microorganisms in modified Friis broth medium decreased thickness of the capsule, but not percentage of cells encapsulated. Marked differences were observed when M ovipeumoniae isolates grown in modified Friis broth medium or co-cultured with ovine fetal lung cells were compared for capsular thickness or percentage of encapsulation. In thin sections of ruthenium red-stained tracheal ring cultures, the mycoplasmas appeared to be in close contact with cilia through their capsule. All isolates of M ovipneumoniae reacted strongly with wheat germ agglutinin lectin. CONCLUSIONS: Mycoplasma ovipneumoniae produces a polysaccharide capsule with variable thickness that is dependent on culture conditions and strain. Morphologic observations suggest that this capsule facilitates adherence of the organism to ciliated epithelium.

Field isolates of Mycoplasma ovipneumoniae exhibit distinct cytopathic effects in ovine tracheal organ cultures.

Ovine tracheal ring explants were infected with four different Mycoplasma ovipneumoniae and one M. arginini field isolate and their ability to induce cytopathic effects was tested by measuring ciliary activity and intracellular calmodulin release. Infected tracheal rings showed significantly decreased ciliary activity as compared to the non-infected control rings. There were, however, marked differences between isolates in the onset and severity of the effects which correlated with their ability to produce hydrogen peroxide. Infected tracheal rings released more calmodulin than the non-infected controls. The amount of calmodulin released also varied between isolates, and somewhat reflected the degree of loss of ciliary activity in the corresponding rings induced by the different isolates. Light and electron microscopic examinations of infected tracheal rings revealed disorganisation and sloughing of the epithelium, and association of mycoplasmas only with the cilia. Following repeated in vitro passages, the organisms had reduced ability to inhibit ciliary activity which correlated with decreased hydrogen peroxide production. Addition of catalase to the organ cultures delayed loss of ciliary activity. These results suggest that M. ovipneumoniae induced ciliostasis in ovine tracheal ring explants which correlated with hydrogen peroxide production. Furthermore, these M. ovipneumoniae-induced injuries to respiratory epithelial cells could contribute to the role that this organism may play in sheep respiratory disease.

Expression of functions by normal sheep alveolar macrophages and their alteration by interaction with Mycoplasma ovipneumoniae.

Normal sheep alveolar macrophages collected by bronchial lavage were exposed to live or heat-killed Mycoplasma ovipneumoniae organisms, and their capability to ingest Staphylococcus aureus and to elicit antibody-dependent cellular cytotoxicity against sensitized chicken red blood cells was tested. Controls consisted of non-infected macrophages in M199 medium. In addition, the effect of M. ovipneumoniae on expression of surface molecules on these sheep alveolar macrophages was determined. The percentage of S. aureus ingested by nontreated sheep alveolar macrophages was significantly higher than that of infected macrophages. Live mycoplasmas were more effective in suppressing the ingestion of S. aureus by these macrophages than killed mycoplasmas. Both live and killed mycoplasmas suppressed the cytolytic effect of the sheep alveolar macrophages to a similar degree. About 78% and 45% of the normal sheep alveolar macrophages had IgG and complement receptors, respectively. Infection of these macrophages with M. ovipneumoniae decreased significantly the expression of IgG receptors but had no effects on complement receptors. There were substantial increases in the expression of both MHC class I and class II by the mycoplasma-induced macrophages as compared with unstimulated macrophages. Live mycoplasmas were more effective in inducing expression of both classes than killed mycoplasmas. The results, taken together, suggest that M. ovipneumoniae induced alterations in macrophage activities and this may be a contributing factor in the pathogenesis of respiratory disease induced by the organism.

Identification of suppressive components in "Haemophilus somnus" fractions which inhibit bovine polymorphonuclear leukocyte function.

"Haemophilus somnus" fractions which inhibited iodination of protein by bovine polymorphonuclear leukocytes were isolated by heat extracting a washed bacterial suspension at 60 degrees C or incubating the bacterial suspension at 37 degrees C and were partially purified by ultrafiltration. The components in each fraction were separated by reverse-phase high-performance liquid chromatography and identified as ribonucleotides, a ribonucleoside, and purine and pyrimidine bases. Most of the compounds were found to be inhibitory to iodination in a dose-dependent manner. When the effect of each component on iodination at the concentrations present in "H. somnus" fractions was determined, it was found that guanine and GMP were the components responsible for most of the suppression in the fraction isolated by heat extraction, whereas guanine and adenine were the major inhibitory components in the fraction isolated by incubation at 37 degrees C.

Haemophilus somnus-induced interference with bovine neutrophil functions.

The effect of Haemophilus somnus on bovine polymorphonuclear leukocyte (PMN) function was examined in vitro with whole cells and fractions extracted from the surface of this bacterium. The ability of PMNs to iodinate protein and ingest Staphylococcus aureus was significantly inhibited in the presence of live cells, heat-killed whole cells or supernatant fluid from heat-killed cells, but not in the presence of washed, heat-killed cells. None of the fractions inhibited nitroblue tetrazolium (NBT) reduction by PMNs. The PMN inhibitory factors were further characterized. The material that inhibited S. aureus ingestion was found to be a heat-stable cell surface material of greater than 300 000 MW. The fraction inhibiting iodination of protein was found to be less than 10 000 MW.

Immunogenicity of potassium thiocyanate extract of type A Pasteurella multocida.

The immunogenicity and cross-protectivity of potassium thiocyanate (KSCN) extracts from Type A Pasteurella multocida strains were evaluated in mice. Mice administered KSCN extracts showed signs of depression for several hours following immunization. These extracts induced protection against challenge with the virulent homologous bacterium although many of the surviving mice were clinically ill up to 72 h after challenge exposure. There was no consistent reciprocal protection between different strains of the serotype indicating lack of correlation between serotype and cross-immunogenicity. Antigenic analysis of KSCN extracts by crossed immunoelectrophoresis techniques revealed greater than or equal to 25 different antigenic components. When the antigenic content of P-2383 and P-1062 KSCN extracts were compared, most antigenic components were common to both; however, two strain-specific and antigenic components were identified with homologous and heterologous antisera. One component present in each of the extracts gave a precipitation line similar to that produced by a crude lipopolysaccharide extracted from the organism. This component was isolated by sucrose density gradient centrifugation. The component isolated from P-2383 KSCN extract sedimented rapidly, indicating a high molecular weight material, and contained 12% carbohydrate and 27% protein. Immunization of mice with this component induced resistance to challenge with the homologous strain and some degree of protection against certain heterologous strains.

Activation of bovine neutrophils by recombinant interferon-gamma.

The effect of recombinant bovine interferon-gamma (r-IFN-gamma) on neutrophil functions was investigated and compared to the effects of an unpurified lymphokine preparation. Incubation of purified bovine neutrophils with r-IFN-gamma or antigen-induced lymphokine for 2.5 hr at 37 degrees C resulted in impairment of the ability of neutrophils to migrate under agarose, and an enhancement of their ability to mediate antibody-dependent and antibody-independent cell-mediated cytotoxicity against chicken erythrocytes. Neither the lymphokine preparation nor the r-IFN-gamma had any influence on Staphylococcus aureus ingestion, or iodination by neutrophils. The lymphokine preparation enhanced cytochrome c reduction by neutrophils and was weakly chemotactic, whereas the r-IFN-gamma had neither of these effects. Only 5 min of r-IFN-gamma preincubation with neutrophils were needed to trigger protein synthesis by the neutrophils resulting in inhibition of random migration. Therefore, recombinant interferon-gamma acts as a neutrophil migration inhibition factor and a neutrophil activation factor resulting in enhanced neutrophil-mediated antibody-dependent and -independent cell-mediated cytotoxicity. Many, but not all, of the in vitro effects of an unpurified lymphokine preparation on neutrophil function can be attributed to the interferon-gamma contained in the lymphokine.

In vivo effect of ascorbic acid on neutrophil function in healthy and dexamethasone-treated cattle.

Ascorbic acid (20 mg/kg of body weight) administered subcutaneously to otherwise nontreated cattle resulted in enhancement of neutrophil oxidative metabolism and capability of neutrophils to mediate antibody-dependent cell-mediated cytotoxicity (ADCC). Random migration, bacterial ingestion, and iodination by neutrophils was unaffected. Three dosage levels of ascorbic acid (10 mg/kg, 20 mg/kg, and 40 mg/kg) were examined for their effects on neutrophil function in cattle treated with dexamethasone (0.04 mg/kg). Dexamethasone administration caused an enhancement of neutrophil random migration and a suppression of neutrophil oxidative metabolism, iodination, and ADCC. None of the dosage levels of ascorbic acid had an effect on the alterations in the WBC count induced by dexamethasone. The ascorbic acid did tend to reverse the effects of dexamethasone on neutrophil random migration, oxidative metabolism, and ADCC in a dose-dependent manner, with the lowest dose having no discernible effect. Ascorbic acid administration also tended to enhance Staphylococcus aureus ingestion by bovine neutrophils. These results indicate that ascorbic acid should be further investigated for its potential to reduce the susceptibility of stressed or glucocorticoid-treated cattle to infective processes.

Activation of neutrophils by antigen-induced lymphokine, with emphasis on antibody-independent cytotoxicity.

Incubation of bovine neutrophils with antigen-stimulated mononuclear cell supernatant (lymphokine) caused an inhibition of neutrophil migration and an enhancement of the neutrophils' ability to adhere to plastic, reduce nitroblue tetrazolium, ingest Staphylococcus aureus, and mediate antibody-dependent cell-mediated cytotoxicity (ADCC) against chicken erythrocytes. Lymphokine-treated neutrophils also became cytotoxic for chicken, turkey and human erythrocytes in the absence of specific antibody but were not cytotoxic for bovine erythrocytes. The increase in antibody-independent neutrophil cytotoxicity (AINC) was not due to direct cytotoxic activity of the lymphokine or to a stable, soluble mediator released by the neutrophils. Enhancement of AINC, but not ADCC, required RNA and protein synthesis by the neutrophil. These results indicate that several aspects of neutrophil function can be altered by products secreted by antigen-stimulated mononuclear cells and that neutrophils can be induced to recognize and to have increased cytotoxic activity toward heterologous erythrocytes.

Enhancement of lymphocyte blastogenesis and neutrophil function by avridine in dexamethasone-treated and nontreated cattle.

The lipoidal amine, N,N-dioctadecyl-N',N'-bis (2-hydroxyethyl) propanediamine (avridine or CP 20,961), formulated in liposomes, was evaluated for its effect on leukocyte kinetics, lymphocyte blastogenesis, and polymorphonuclear leukocyte (PMN) function in dexamethasone-treated and nontreated cattle. In the 1st experiment, cattle were given avridine in a single IM injection of 0.1, 1.0, or 10 mg/kg of body weight. All doses induced swelling at the injection site, a febrile response, and a leukocytosis due to a neutrophilia. Mononuclear cell numbers were normal. All 3 groups of avridine-treated animals had a higher mean lymphocyte blastogenic response to mitogens on the 4 days after administration than did the control nontreated animals. Avridine administration was associated with an enhanced ability of PMN to ingest Staphylococcus aureus and to mediate antibody-dependent cell-mediated cytotoxicity (ADCC). The highest dose (10 mg/kg) was associated with a depression of the ability of PMN to iodinate protein. An effect of avridine on PMN random migration under agarose or nitroblue tetrazolium (NBT) reduction was not observed. In a 2nd experiment, cattle were given no treatment, 0.04 mg of dexamethasone/kg IM, or 10 mg of avridine/kg IM followed 24 hours later by 0.04 mg of dexamethasone/kg. Dexamethasone administration caused a leukocytosis due to a neutrophilia with normal mononuclear cell numbers, an enhancement of PMN random migration under agarose, and an inhibition of NBT reduction, iodination, and ADCC activity of PMN. Dexamethasone did not have a detectable effect on lymphocyte blastogenesis or on ingestion of S aureus by PMN.(ABSTRACT TRUNCATED AT 250 WORDS)

Attempts to use thiabendazole to improve the immune response in dexamethasone-treated or stressed cattle.

Thiabendazole was evaluated in two separate experiments for its ability to enhance the immune response in dexamethasone-treated or stressed cattle. In the first experiment the cattle received either no drug treatment (controls), dexamethasone intramuscularly (IM), or dexamethasone IM plus thiabendazole orally. All animals were inoculated with heat-killed Brucella abortus strain 19, equine ferritin, tetanus toxoid, and live Corynebacterium equi at the time dexamethasone therapy was initiated. Dexamethasone (0.04 mg/kg/day IM for 3 days) significantly (p less than 0.05) inhibited the lymphocyte blastogenic response to mitogens and the antibody response to ferritin and tetanus toxoid. Thiabendazole given orally (16 mg/kg/day) beginning 24 h prior to antigen and dexamethasone administration and continued for 6 days failed to prevent the dexamethasone-induced suppression of the lymphocyte blastogenic or antibody responses. In the second experiment 51 cattle were divided into a control group and a thiabendazole-treated group. The animals were stressed by weaning, injection of antigen (equine ferritin, tetanus toxoid, B. abortus strain 19 and killed bovine viral diarrhea virus) and castration of the bulls on the day that thiabendazole therapy was started. Thiabendazole administered orally for 5 days at a dosage of 20 mg/kg did not enhance the antibody response to any of the antigens, and was associated with a significantly lower antibody response to B. abortus.

Effects of thiabendazole on dexamethasone-induced suppression of lymphocyte and neutrophil function in cattle.

Seven dosage levels of thiabendazole were evaluated for their ability to normalize lymphocyte or neutrophil function in dexamethasone-treated cattle. Dexamethasone administration (0.04 mg/kg intramuscularly daily for 3 days) significantly suppressed the lymphocyte blastogenic response to phytohemagglutinin, concanavalin A, and pokeweed mitogen. The lymphocyte blastogenic response to allogeneic lymphocytes was also suppressed in dexamethasone-treated cattle, but this effect was not statistically significant. Neutrophils from dexamethasone-treated cattle had a significantly enhanced ability to migrate under agarose, and significantly suppressed ability to reduce nitroblue tetrazolium, iodinate protein, and mediate antibody-dependent cell-mediated cytotoxicity. Thiabendazole when administered concurrently with dexamethasone in the dosage range from 1.0 to 25.0 mg/kg (orally) did significantly enhance lymphocyte blastogenic responsiveness to phytohemagglutinin, concanavalin A, pokeweed mitogen and allogeneic cells (in dexamethasone-treated cattle). This immunonormalizing effect was not observed at the 50 or 100 mg/kg dosage levels. Thiabendazole did not produce a consistent significant enhancement of any parameter of neutrophil function in dexamethasone-treated cattle.

Equine cell-mediated immune response to Rhodococcus (Corynebacterium) equi.

A lymphocyte blastogenic assay was developed to serve as an in vitro correlate of cell-mediated immunity to Rhodococcus (Corynebacterium) equi (R equi) in the equine species. Lymphocytes obtained from a group of experimental ponies showed no response in cell culture to R equi heat extract or lysozyme extract antigens. Ponies were assigned to groups for experimental inoculation. Three ponies were inoculated subcutaneously with live R equi, 3 were given live R equi by intranasal and intratracheal routes, and 4 ponies were left untreated. Lymphocytes from all inoculated ponies had a mitogenic response to R equi antigens in lymphocyte blastogenic assays performed between the 7th and 40th days after inoculation. Lymphocytes from noninoculated control ponies remained unresponsive to R equi antigens. Delayed-type hypersensitivity reactions developed in all experimentally exposed ponies after intradermal administration of the R equi antigen preparations. In a 2nd phase of experimentation, blastogenesis assays were performed on lymphocytes from horses in herds with endemic R equi infections. Results indicated that many of the animals had significant (stimulation index greater than 2) cell-mediated responses to the bacterium, but there was no distinct correlation between the immune response and clinical history. These data indicated that cell-mediated immunity is involved in the interaction of the equine immune system with R equi.

Equine humoral immune response to Rhodococcus (Corynebacterium) equi.

An enzyme-linked immunosorbent assay was developed to test equine serum for the presence of antibodies to Rhodococcus (Corynebacterium) equi. Experimental ponies had no detectable antibody to R equi before exposure to the bacterium. After experimental inoculation, animals in groups that received live R equi subcutaneously or intranasally/intratracheally developed high titers to R equi. Noninoculated controls remained seronegative. Serum was also collected from horses of various ages that were naturally exposed to R equi. There was a wide range of anti-R equi titers in these horses. Because experimentally infected horses seroconverted when some naturally infected foals did not seroconvert, the function of antibody in resistance to R equi infection remains unknown.

Effect of Rhodococcus equi on equine polymorphonuclear leukocyte function.

A procedure was developed for isolating large numbers of purified polymorphonuclear leukocytes (PMNs) from the peripheral blood of horses. Equine PMN function was evaluated by three procedures: 1) Staphylococcus aureus ingestion, 2) nitroblue tetrazolium reduction, and 3) iodination. Four preparations of R. equi were added to polymorphonuclear leukocytes (PMNs) in each test system. Live bacteria, heat-killed bacteria, the washed pellet from heat-killed bacteria, and the supernatant fluid from heat-killed bacteria were evaluated for effects on equine PMN function. None of the R. equi preparations had an effect on S. aureus ingestion by equine PMNs. Nitroblue tetrazolium reduction by PMNs, a measure of oxidative metabolism, was suppressed by pellet and supernatant fractions. Values for the iodination reaction were depressed by all R. equi preparations, indicating decreased activity of the myeloperoxidase-H2O2-halide system of the PMN. Further evaluation of the supernatant from heat-killed R. equi showed that it retained its inhibitory effect on iodination following autoclaving and/or passage through a 10,000 MW filter. R. equi fractions did not alter the enzymatic conversion of 125I to a protein-bound form in a PMN-free assay developed to evaluate this reaction. The presence of a surface component capable of inhibiting bactericidal mechanisms of the PMN may play an important role in intracellular survival of R. equi.

Effect of levamisole on lymphocyte blastogenesis and neutrophil function in dexamethasone-treated cattle.

Levamisole was evaluated at 6 dose levels for its ability to prevent the dexamethasone-induced suppression of in vitro lymphocyte blastogenesis or neutrophil function in cattle. Dexamethasone (0.4 mg/kg of body weight, IM) and levamisole hydrochloride (0.5, 1.0, 2.0, 4.0, or 8.0 mg/kg orally) were administered to groups of 4 cattle daily for 3 days. Another group of 4 cattle were given the 3-day dexamethasone treatment and 6.0 mg/kg of levamisole (the recommended anthelmintic dose) was given only once on the 1st day that dexamethasone was given. Results obtained from the dexamethasone-levamisole-treated cattle were compared with results obtained from cattle that were given only dexamethasone. Levamisole had no apparent consistent ability to enhance lymphocyte blastogenic responsiveness (to the mitogens phytohemagglutinin, concanavalin A, or pokeweed mitogen or in a 1-way mixed lymphocyte reaction) or to enhance neutrophil function (random migration, nitroblue tetrazolium reduction, iodination, or antibody-dependent cell-mediated cytotoxicity) in dexamethasone-treated cattle.