GAMMA-DELTA T-CELLS DOWN-REGULATE PRIMARY IGE RESPONSES IN RATS TO INHALED SOLUBLE-PROTEIN ANTIGENS

The biologic role and repertoire of cells bearing the gamma delta T ce ll receptor has not been fully defined. However, their tropism for epi thelial microenvironments is recognized and suggests an important role for these cells in immune defense at mucosal tissue surfaces. The stu dy presented below utilizes an experimental model in which repeated ex posure of Brown Norway rats to OVA by inhalation induces a state of Ag -specific, IgE isotype-specific ''tolerance'' via immune deviation. Th is process seems similar to oral tolerance in the gut. This form of to lerance was adoptively transferred to naive syngeneic recipients by i. p. injection of as few as 10(3) positively selected TCR-gamma delta(+) cells from OVA-exposed rats. These TCR-gamma delta(+) T-cells are dem onstrated to produce high levels of INF-gamma in response to OVA stimu lation, and this provides a potential mechanism for the inhibition of Th2 cell proliferation, resulting in suppression of IgE production. Th e unique potency of these cells in selective suppression of IgE Ab pro duction in response to natural ''mucosal'' Ag exposure suggests a pote ntially important role in protection against primary allergic sensitiz ation in vivo.