Antigen specific stimulation of immune responses during long-term repeated skin testing with multiple antigens

Delayed-type hypersensitivity (DTH) skin testing as an assay of immune competence is a widely used technique. Accordingly, clinical situations frequently occur which require that skin tests be performed many times on the same patient. In the present investigation, in vivo and in vitro immune responses were studied over a 7-month period in 22 normal human volunteers, each of whom were skin tested 6 times at monthly intervals with multiple antigens. Patterns of responses to the 7 specific skin test antigens observed during repeated skin testing in vivo indicated non-significant, but detectable, declines in skin test reactivity to tetanus, diphtheria and streptococcus antigens and increases in reactivity to trichophyton, tuberculin, candida and proteus antigens. In vitro lymphocyte transformation assays (LTAs) of cell-mediated immune (CMI) activities revealed that repeated skin testing, e.g., 3-5 serial skin tests, induced significantly increased levels of CMI reactions with 3 of the 4 skin test antigens used as challenge antigens. Since no significant changes in in vitro CMI responses were detected using 3 control "non-skin test" antigens, the effects observed were confirmed to be antigen specific. Increased IgG antibody responses were detected for only the toxoid antigens during the skin testing period. For the group of 22 normal volunteers, positive statistical correlations were not observed between any individual skin test antigen and the immune reactions assayed specifically for that antigen, including DTH responses and levels of circulating antigen-specific antibodies. Short term differences were detected between tetanus, diphtheria and streptococcus antigens in their LTA response patterns.(ABSTRACT TRUNCATED AT 250 WORDS)