Lymphatic cannulation and serial biopsy were used to examine changes in cell traffic and lymphocyte populations after injection of adjuvant in order to explain the mechanisms of the subversive effect that Freund's adjuvants (FA) have on protective immunity against nematode parasites in sheep. Within 4 days of intradermal injection of complete or incomplete FA into sheep there was a selective depletion of the T19+ TCY gamma delta+ T lymphocyte subpopulation from efferent lymph draining the local lymph node. Transient depletion of CD8+, T19+ and CD5+ cells from jugular blood was evident at day 2. The adjuvant-induced granuloma was a connective tissue/macrophage/T lymphocyte phenomenon, with no B cell follicles, and the T cell content continued to increase for the 21 days. The early granuloma (days 2-4) contained a disproportionate number of T19+ gamma delta + lymphocytes. It appeared that the adjuvants induced selective sequestration of this T cell subset during the initial period of granuloma formation.