Serum dioxin and immunologic response in veterans of operation ranch hand

The authors studied immune response and exposure to 2,3,7,8-tetrachlorodibe nzo-p-dioxin (dioxin) among veterans of Operation Ranch Hand, the US Air Fo rce unit responsible for the aerial spraying of herbicides in Vietnam from 1962 to 1971. A comparison group of Air Force veterans who served in Southe ast Asia but were not involved in spraying herbicides was included. The aut hors studied delayed-type hypersensitivity skin test responses to Candida a lbicans, mumps, Trichophyton, and a bacterial antigen made from lysed Staph ylococcus aureus, Lymphocyte measurements included total lymphocyte counts; T-cell (CD3, CD4, CD5, and CD8), B-cell (CD20), and NK-cell (CD16 and CD56 ) subsets; and expression of the activation antigen CD25 on CD3 T cells. Th e authors quantitated the serum concentrations of immunoglobulin (Ig)A, IgG , and IgM; examined sera for the presence of monoclonal immunoglobulins (M proteins); and looked for a broad range of autoantibodies (rheumatoid facto r, antinuclear antibody, smooth muscle autoantibody, mitochondrial autoanti body, parietal cell autoantibody, and thyroid microsomal autoantibodies), T hey measured the level of dioxin in 1987 or 1992, extrapolated the result t o the time of service in Vietnam, and assigned each veteran to one of four exposure categories: Comparison and three Ranch Hand groups (Background, Lo w, or High). Overall, the authors found no evidence of a consistent: relati on between dioxin exposure category and immune system alteration.