complement activation by mycoplasma

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Infect Immun 2000 Mar;68(3):1672-80

Complement activation in Mycoplasma fermentans-induced mycoplasma

clearance from infected cells: probing of the organism with

monoclonal antibodies against M161Ag.

Kikkawa S, Matsumoto M, Sasaki T, Nishiguchi M, Tanaka K, Toyoshima

K, Seya T

Department of Immunology, Osaka Medical Center for Cancer and

Cardiovascular Diseases, Higashinari-ku, Osaka 537-8511, Japan.

Mycoplasma fermentans, a cell wall-less prokaryote, is capable of

infecting humans and has been suggested to serve as a cofactor in

AIDS development. Recently, we discovered a novel lipoprotein with a

molecular mass of 43 kDa originating from M. fermentans. This

protein, named M161Ag, activated human complement via the alternative

pathway and efficiently induced the proinflammatory cytokines

interleukin 1beta (IL-1beta), tumor necrosis factor alpha, IL-6, IL-

10, and IL-12 in human peripheral blood monocytes. It is likely that

M161Ag of M. fermentans affects the host immune system upon

mycoplasma infection. In this study, we developed monoclonal

antibodies (MAbs) against M161Ag and examined the direct role of

complement in M. fermentans infection using these MAbs as probes. M.

fermentans was rapidly cleared from the surfaces of infected cells by

human complement, but a low-grade infection persisted in human tumor

cell lines. Mycoplasma particles remaining alive in host cells may

cause recurrent infection, and liberated M161Ag may serve as a

biological response modifier affecting both innate and acquired

immunity.