Characterization of γδ T Cells Expressing CD158b, a Killer Cell Inhibitory Receptor, in a Patient with Chronic CD4+ Lymphocytopenia and Disseminated Mycobacterium intracellulare Infection

A population of Vδ1+Vγ9− γδ T cells that represented almost the totality (84%) of circulating lymphocytes in a patient with chronic, non-HIV-related, CD4 lymphocytopenia complicated by a disseminated Mycobacterium intracellulare infection was characterized. These γδ+ T cells expressed a single killer inhibitory receptor (CD158b) and their phenotype (CD8+CD57+CD27−CD28−) indicated that, although CD45RA+, they were not naive. However, the absence of large granular lymphocyte morphology, the impaired proliferative activity, the high susceptibility to apoptosis, and the total lack of cytotoxic ability suggested that these γδ cells were in a resting state. A high percentage of the cells did not harbor the CD11b integrin α chain and exhibited a decreased capability to bind endothelial cells. This defect might represent the mechanism whereby they remained trapped in the circulation.