To evaluate humoral and cellular immune responses in the genital tract following oral administration, live oral typhoid vaccine Ty 21a (Vivotif Berna) was given to 10 healthy female volunteers (aged 24 - 39 years). Samples of peripheral blood were collected from 9 of these volunteers between days 4 and 11 post immunization and the mononuclear cells were isolated. ELISPOT analysis of antibody-secreting cells (ASC) against Salmonella typhi O -9,12 antigen showed that 8 out of 9 volunteers responded in all 3 major isotypes, and in 4 out of 8 subjects the responses were dominated by IgA. In 3 out of the 6 volunteers evaluated, 100% of ASC expressed o407 homing receptor, and considerably fewer were positive for L-selectin. Only a slight increase in specific antibodies (mostly IgG) against the immunogen was observed in sera of 7 out of the 10 volunteers. The secretions (saliva, vaginal lavage, and cervical mucus) collected before, and 3 times after immunization (at mid-cycle) also displayed a small increase in salivary (4/10), vaginal (5/10), and cervical (4/10) IgA. The results obtained suggest that antibodies in the human female genital tract induced by oral administration of vaccines are not plasma derived, but are locally produced by cells which are sensitized in the gut and migrate through the peripheral circulation to other mucosal sites.