Receptors for opsonins, such as complement component C3b (CR1) and immunoglobulins, Fc receptors, interact with adhesion glycoproteins in mediating immune functions. Defects in expression of the adhesion glycoproteins CD11/CD18 results in severely hampered in vitro and in vivo adherence-related functions of leukocytes. Little is known regarding the effect of leukocyte adhesion deficiency (LAD) on ligand binding and receptor expression. We investigated the binding and expression of CR1 and Fc receptors by bovine neutrophils isolated from dairy calves suffering from LAD, compared with clinically normal (hereafter referred to as normal) age-matched calves. Neutrophils were also assayed for endogenously bound IgG and IgM and for exogenous binding of C3b, IgG1, IgG2, IgM, and aggregated IgG (aIgG), using flow cytometry. Luminol-enhanced chemiluminescence (CL) production in response to IgG2 opsonized zymosan was studied, and specific inhibition of CL was used to determine the specificity of IgG2 binding. Activation of protein kinase C with phorbol myristate acetate was used to determine the effect of cellular activation on expression of CR1. A greater percentage of neutrophils from normal calves bound C3b than did neutrophils from LAD-affected calves. Receptor expression was similar. Activation with phorbol myristate acetate resulted in increased expression of CR1 on neutrophils from normal and LAD-affected calves, but expression was almost twofold greater on neutrophils from normal calves. There was no difference between LAD-affected and normal calves in percentage of neutrophils that bound endogenous IgG and IgM. A greater percentage of neutrophils from normal calves bound exogenous IgM than did neutrophils from LAD-affected calves. Receptor expression for aIgG was greater on neutrophils from LAD-affected calves than on those from normal calves.

Cytologic examination of bronchoalveolar lavage fluid (BALF), including phenotypic analysis of lymphocytes, was performed on 32 Standardbreds with poor race performance and endoscopic examination findings characteristic of inflammatory airway disease (IAD). Nucleated cell counts in BALF from IAD-affected horses were higher than those in control horses; the cytologic profile of BALF in affected horses included mixed inflammation, characterized by mild neutrophilia, lymphocytosis, and monocytosis. Eosinophil and mast cell counts were not higher in the IAD-affected group, compared with those in the control group; however, 4 IAD-affected horses had marked eosinophilia (24.7 +/- 4.8% SEM) in BALF. Phenotypic analysis of lymphocytes in BALF obtained from IAD-affected horses revealed a low proportion of CD4-positive cells and B cells, compared with those in the control group; these findings may have been representative of a greater proportion of non-B, non-T cells (null cells) in horses with IAD. The cytologic profile of BALF obtained from horses with IAD differed from that in horses affected with chronic obstructive pulmonary disease, suggesting that the pathogenesis of inflammation in horses with IAD may differ from that of chronic obstructive pulmonary disease.

Bovine immunodeficiency virus (BIV) is prevalent in beef and dairy cattle, yet the mode(s) of BIV transmission are undefined. Using polymerase chain reaction, which specifically targeted a 235-bp, highly conserved region of the BIV pol gene, BIV-infected leukocytes were detected in the blood and milk of BIV-seropositive cows. These data confirm the presence of BIV in milk and identify the potential for lactogenic transmission of this virus.

Cytologic examination of bronchoalveolar lavage fluid (BALF), including phenotypic analysis of lymphocytes, was performed on 32 Standardbreds with poor race performance and endoscopic examination findings characteristic of inflammatory airway disease (IAD). Nucleated cell counts in BALF from IAD-affected horses were higher than those in control horses; the cytologic profile of BALF in affected horses included mixed inflammation, characterized by mild neutrophilia, lymphocytosis, and monocytosis. Eosinophil and mast cell counts were not higher in the IAD-affected group, compared with those in the control group; however, 4 IAD-affected horses had marked eosinophilia (24.7 +/- 4.8% SEM) in BALF. Phenotypic analysis of lymphocytes in BALF obtained from IAD-affected horses revealed a low proportion of CD4-positive cells and B cells, compared with those in the control group; these findings may have been representative of a greater proportion of non-B, non-T cells (null cells) in horses with IAD. The cytologic profile of BALF obtained from horses with IAD differed from that in horses affected with chronic obstructive pulmonary disease, suggesting that the pathogenesis of inflammation in horses with IAD may differ from that of chronic obstructive pulmonary disease.

Bovine immunodeficiency virus (BIV), a lentivirus, is prevalent in dairy and beef cattle in southeastern United States and may be associated with a lymphoproliferative disease. The mode(s) of BIV transmission are undefined. Because artificial insemination is a common practice in dairy production, contaminated stud semen could serve as an important source of infection if the virus is harbored in seminal fluids. To evaluate this possibility, we procured 11 cryopreserved semen specimens from a stud semen repository. Leukocytes were purified from the specimens, and the leukocyte DNA was used as template in a polymerase chain reaction procedure that targeted a 235-base pair, highly conserved domain of the BIV pol gene. The target sequence was amplified from the seminal leukocyte DNA of 9 of the specimens (82%), and nucleotide sequencing confirmed the BIV specificity of the fragment. This finding provides evidence that stud bull semen may serve as an important reservoir of BIV, suggesting the possibility that artificial insemination of dairy cows may have a major role in transmission and wide-spread dissemination of this bovine lentivirus.

The effect of oxytetracycline (OTC) on bovine blood mononuclear cells and neutrophil functions was examined in vitro. Neutrophil functions tested include respiratory burst, peroxidase, and antibacterial activities. Neutrophils were treated with OTC (10 to 1,500 > microgram/ml) before exposure to either opsonized zymosan or bacteria. A dose-response inhibition of antibacterial activity to high concentrations of OTC (500 to 1,000 microgram/ml) was observed. Beginning at a concentration of 15 microgram/ml, OTC treatment of neutrophil Iysates resulted in decreased peroxidase activity. A dose response was not observed. In contrast, respiratory burst, measured by nitroblue tetrazolium dye reduction, increased after OTC exposure, but only at high concentrations (500 and 1,000 microgram/ml) of OTC. Mitogen-induced proliferation of blood mononuclear cells cocultured with OTC and concanavalin A, phytohemagglutinin-P, or pokeweed mitogen was inhibited at an OTC concentration of 100 microgram/ml at 48 and 72 hours of culture. These results indicate that blood mononuclear cells are more sensitive to the inhibitory effects of OTC than are neutrophils. Furthermore, the OTC-mediated inhibition of neutrophil antimicrobial activity is inversely related to the increase in nitroblue tetrazolium reduction. This suggests that OTC is uncoupling the hexose monophosphate shunt from production of secreted oxygen radicals. These results also suggest that the peroxidase enzyme system has a large biological reserve capacity.