T lymphocytes (CD4 and CD8) responsible for “protective cellular immunity” activate the cell-mediated immune reaction, while B lymphocytes are responsible for the massive and differentiated production of antibodies (class M, A, D, E, and G immunoglobulins) as humoral immunity, which lasts over time, with a high antibody titer and sterilising immunity that would prevent a second infection [357,358,359]. The gene discussed is CD4; the disease is infection.