Interactions of lymphocytes with bacterial antigens.

Several observations indicate that smooth (S) and rough (R) Salmonella strains display the capacity to spontaneously adhere to lymphoid cell membrane. Such a phenomenon is confined to T lymphocytes and affects both CD4+ and CD8+ cells. As far as receptor structures on lymphocytes surface are concerned, the lipopolysaccharides (LPS) of the bacterial cell wall play a key role in human and murine cytoadherence. In addition, evidence has been provided that LPS of gut flora induce bacterial binding as assessed by the evaluation of cyto-adherence at different anatomical sites. Interestingly, cells mediating nonspecific immune responses are not involved in the bacterial binding, since the unbound fraction is highly enriched for cytotoxic and T helper cells. The in vivo occurrence of binding in typhoid fever patients suggests that this activity may represent an earlier event during the course of infection. These findings are also supported by the demonstration that chemotherapeutic treatment abolished bacterial binding in both vitro and in vivo systems. Finally, the production of lymphokines following bacterial stimulation points out the importance of bacterial/immune system interaction in the development of immune response during gram-negative sepsis.