Immune responses in Mycoplasma bovoculi conjunctivitis

Calves infected with Mycoplasma bovoculi respond with conjunctivitis, extensive colonization of cell-adherent mycoplasmas, and a transient influx of neutrophils to ocular surfaces. Antibody responses can be detected in the circulation and in lacrimal fluid by enzyme-linked immunosorbent assay (ELISA). Serum responses were primarily IgM and IgG and included complement-independent metabolic inhibition activity, while lacrimal fluid responses were primarily IgA and did not exhibit metabolic inhibiting activity. Cell-mediated immune responses also followed the initial infection. In all cases, these immune responses were concurrent with persistent colonization of ocular surfaces. Clearance of persistent infections was observed after variable periods of time and was followed by resistance to challenge. Parenteral presentation of antigen gave similar systemic responses with no lacrimal responses. Animals given antigen parenterally exhibited inflammatory responses and persistent colonization after challenge. These reactions were more intense than those following infections in unstimulated cattle.