Cell-mediated immunity to bacterial flagellin as assessed by leucocyte adherence inhibition

Leucocyte adherence inhibition (LAI) was used to detect cell-mediated immunity of mice to Salmonella adelaide polymeric flagellin and its monomeric derivative. In the direct LAI technique, antigen inhibited the in vitro adherence to glass of peritoneal cells (PC) from antigen-primed mice which were capable of exhibiting in vivo delayed hypersensitivity reactions to the same antigen. In the indirect technique, primed PC exposed to antigen in vitro released a soluble factor, which inhibited the adherence of normal PC. Production of the factor was prevented by prior treatment of primed PC with anti-theta serum, indicating the participation of T-lymphocytes. The LAI reaction could be blocked by serum from mice which had been re-injected with antigen 72 h after a priming injection. Features of the production and biological properties of serum blocking activity suggest that it may be attributed to antigen-antibody complexes.