One of Dr. Yueh-hsiu Chien's main research focuses is to define γδ T cell function so that we can better understand host immune defense. γδ T cells, together with B cells and αβ T cells, are the only cells that use somatic V, D, J gene rearrangement to generate diverse antigen receptors. All three types of cells are present together in all but the most primitive vertebrates, suggesting that each population contributes to host immune competence uniquely and that all three are necessary for maintaining immune competence. Functional analysis indicates that in infections, γδ T cells respond earlier than αβ T cells do; and also emerge late after pathogen numbers start to decline. Thus, these cells may be involved in both establishing and resolving the inflammatory response.

Dr. Chien's group's past studies indicate that γδ T cells and αβ T cells are clearly distinct in their antigen recognition and activation requirements and also in antigen-specific repertoire and effector-function development. These aspects allow γδ T cells to occupy unique temporal and functional niches in host immune defense. The group is following up on these studies to determine how γδ T cell function affect the development and the termination of the inflammatory response and to study γδ T cells function in infections and autoimmune diseases. These include a mouse model of Toxoplasma gondii infection (in collaboration with Dr. John Boothryod) and celiac patients in response to gluten challenge (in collaboration with Dr. Mark Davis). Dr. Chien's group will expand the analysis to TB patients.