Changes in non-specific immune responses induced by repeated delayed-type hypersensitivity skin testing with multiple antigens

Delayed-type hypersensitivity (DTH) responses following in vivo multiple-antigen skin testing in healthy individuals have been well described as indicators of immune responsiveness. In contrast, little information is available about how repeated in vivo multiple antigen skin testing could effect major non-specific parameters of immune responses. In a prospective study of 22 healthy adult volunteers, DTH skin tests were performed 6 times at 4-week intervals over a 28-week course. Prior to each skin test, blood specimens were collected and evaluated by in vitro assays of non-specific parameters related to humoral and cell-mediated immune (CMI) responses. Sustained effects of repeated skin tests in the volunteers included decreased numbers of circulating polymorphonuclear leukocytes (PMNLs), increased serum IgM levels and decreased DTH responses in those individuals originally designated as high DTH responders. Increased lymphocyte transformation with PHA was transiently observed in the study group at 4-12 weeks into the study. In contrast, numbers of T, B and total lymphocytes, levels of IgG, IgA, and circulating immune complexes, and serum blocking activity did not change. This study suggests that few alterations in non-specific immune parameters may be expected to occur in normal, adult individuals as a result of repeated multiple-antigen skin tests.