A study of humoral and cell-mediated immune response following typhoid vaccination in human volunteers.

The specific antibody response to O, H and Vi antigens, levels of IgG, IgM, IgA, and C3 presence of soluble immune complexes, in vitro tests of cellular immunity and subsets of lymphocytes in the peripheral blood were investigated in human volunteers after a single dose of 0.1 ml intradermal typhoid vaccination. The results indicated that typhoid vaccination induced antibody formation, slightly increased IgA levels and led to a decrease in C3 which was probably due to immune complex formation. There was also a relative increase in circulating Fc-IgG receptor-bearing lymphocytes and T-gamma cells after vaccination. In those subjects who showed specific cellular immunity before vaccination, a transient depression in lymphocyte transformation and a negative leucocyte migration inhibition test with typhoid baccilli occurred post-vaccination. These findings raised doubts over the advantages of giving typhoid vaccine during an epidemic.