MONOCLONAL-ANTIBODIES THAT INHIBIT MITOGENIC ACTIVITY OF MYCOPLASMA-PULMONIS

Previous studies have suggested a correlation between mitogenic, polyc lonal activation of host lymphocytes and the respiratory tract inflamm atory diseases induced by Mycoplasma pulmonis. This study describes th e generation of monoclonal antibodies (MAbs) to M pulmonis membrane an tigens with different capacities to inhibit stimulation of cultured ra t lymphocytes by mycoplasmal membranes and with variable effects on M. pulmonis growth. We show that the inhibitory effects exerted on mitog enesis by purified MAbs are inversely related to the effects of MAbs o n Ri. pulmonis growth. Immunoblotting of electrophoretically separated membrane proteins, with both growth- and mitogenesis-inhibiting antib odies, revealed significant changes in the reactions obtained with bot h types of MAb following short exposure of membranes to heat. Growth-i nhibiting MAbs strongly react with heat-labile antigenic complexes wit h molecular weights of 65,000 to 75,000. Inhibition of mitogenesis is mainly associated with recognition of membrane complexes of 84 to 113 kDa that exhibit disperse smears and variable heat sensitivities, Foll owing brief heating of membranes, more distinct bands of 103, 90, and 84 kDa are obtained with MAbs that inhibit mitogenesis. Experiments wi th other mitogenic mycoplasma species and MAb 3.3.10.2, a potent inhib itor of mitogenesis reveal that whereas the antigenic epitope recogniz ed by this antibody is present on unheated membranes from different my coplasmas, with heated membranes the MAb yields reactions only with M. pulmonis and M. arthritidis, Our studies suggest that M. pulmonis mit ogens are unique membrane complexes of variable molecular weights, hig hly susceptible to heat and less sensitive to reducing agents.