Clonal expansion of Vγ3/Vδ3-expressing γδ T cells in an HIV-1/2-negative patient with CD4 T-cell deficiency

Immunological investigations were carried out in an HIV-1/2//HTLV-1-negative patient with CD4 T-cell deficiency (0.357–0.6 × 10⁹/l) and expansion of γδ T cells which accounted for 26–42% of peripheral blood lymphocytes during an observation period of 3 years. Flow cytometry analyses with a panel of available Vγ/Vδ-specific monoclonal antibodies indicated that the pathologically expanded γδ population expressed Vγ2 or Vγ3 paired with Vδ3 on the surface but lacked the expression of activation antigens such as CD38 or CD71. Cloning and sequencing of RT-PCR products obtained after amplification of cDNA with Vγ-Cγ and Vδ-Cδ specific primers confirmed the presence of a clonally expanded Vγ3/Vδ3 population in the peripheral blood of this patient. Cytotoxicity assays performed with purified γδ T cells as effectors and resting or preactivated autologous CD4 T cells as targets failed to reveal evidence for autoreactive cytotoxicity of Vγ3/Vδ3 cells as a possible mechanism of CD4 T-cell deficiency in this patient.