For example, immunological measurements have shown that (1) HIV-induced lymphopenia in HIV-TB patients was associated with reduced anti-viral antibody levels and frequencies of SARS-CoV-2-specific CD4+ T cells; (2) active TB was associated with reduced polyfunctionality of SARS-CoV-2-specific CD4+ T cell responses; and (3) acute SARS-CoV-2 infection diminished the pool of M. tuberculosis-specific memory T cell responses (Riou et al., 2021), possibly due to SARS-CoV-2-induced lymphopenia (Shariq et al., 2022). This evidence concerns the gene CD4 and lymphopenia.