Macrophages interact with enriched populations of distinct T lymphocyte subsets for the induction of severe destructive Lyme arthritis.

Severe destructive Lyme arthritis was detected in the hind paws of hamsters infused with enriched populations of either CD4 1 or CD4 2 T lymphocytes along with macrophages exposed in vitro to formalin-inactivated Borrelia burgdorferi and then infected with the Lyme spirochete. Swell- ing was detected 4 days after infection, increased rapidly, peaked on day 8 of infection, and gradually decreased. Similarly, severe destructive arthritis was induced in hamsters infused with enriched populations of unfractionated T lymphocytes and macrophages exposed to spirochetes after infection with B. burgdorferi. Histopathological examination affirmed that hamsters infused with CD4 1 , CD4 2 , or unfractionated T lymphocytes and macrophages exposed to B. burgdorferi-induced arthritis. In addition, macrophages exposed in vitro to B. burg- dorferi demonstrated both conventional and coiling phagocytosis, suggesting a mechanism by which CD4 1 and CD4 2 T lymphocytes induce arthritis, respectively. These findings demonstrate that both CD4 1 and CD4 2 subpopulations of T lymphocytes are capable of interacting with macrophages for the induction of severe destructive Lyme arthritis. J. Leukoc. Biol. 65: 162-170; 1999.