Single cell analysis of T cells, focused on NK cell receptors and signaling molecules, such as KIRs, NKp30, NKG2C, CD16, NKG2D, and FcεRIγ, may provide valuable insights into the role of such “innate-like” T cell subpopulation in the development of COVID-19 and other viral infections. The gene discussed is KLRD1; the disease is viral infectious disease.