Lyme disease is a tick borne, multi-system disorder caused by low density systemic infections with the spirochete Borrelia burgdorferi. Without antimicrobial treatment, mammalian infections with these bacteria are persistent and chronic. Recent studies showed that B. burgdorferi can target, invade, and lyse both cultured and primary human B and T cells. Direct interactions between the spirochetes and lymphocytes also leads to adherence of B and T cell antigens on the surface of significant proportions of the bacteria . Adherent lymphocytic antigens inhibit binding of antibodies to prominent B. burgdorferi proteins, and interfere with classic complement-mediated killing, suggesting a possible role for spirochete-lymphocyte interactions in immune evasion.

In order to develop an experimental animal model for assessing spirochete-lymphocyte interactions, B. burgdorferi and primary mouse lymphocytes were co-incubated and examined by electron microscopy. Mononuclear cells were separated from fresh mouse blood by Ficoll gradient centrifugation (ICN, Biomedicals, Aurora, Ohio).