MECHANISMS OF ATTACHMENT OF MYCOPLASMA-ARTHRITIDIS TO HOST-CELLS INVITRO

Although other investigators have reported that Mycoplasma arthritidis failed to attach to several types of mammalian cells in vitro, we showed that it attached well to rat synovial fibroblasts, lung cells, and skin cells but not to kidney cells, suggesting that receptor sites are unequally expressed or distributed among different rat tissues. M. arthritidis also attached poorly to canine kidney and to baby hamster kidney cells, although it did attach to human fetal lung and fetal amnion cells. Four M. arthritidis strains, two virulent and two avirulent, all attached equally well to rat lung cells. Attachment was inhibited by trypsinization, suggesting that the major adhesins are protein. Fab' fractions of rabbit antisera against four M. arthritidis strains partially inhibited adherence of both homologous and heterologous strains, although not to the same extent, indicating some degree of antigenic heterogeneity among their adhesins. A filter-cloned variant of M. arthritidis 158p10p9, designated LC1, attached poorly compared with the parent strain. Missing from this variant were two proteins migrating within the 81- to 90-kDa range by polyacrylamide gel electrophoresis; in their place was a 24-kDa antigen that may be a truncated version of one of these proteins. A monoclonal antibody that partially inhibited attachment recognized all these peptides by Western immunoblotting. An additional attachment-inhibiting monoclonal antibody recognized a 71-kDa antigen present in both low-adherence and fully adherent populations. The low-adherence variant LC1 induced slightly but significantly less arthritis in Lewis rats than did a fully adherent clone.