We therefore conclude that the CD4+ and B cell lymphopenia measured in the LN, decreased Th1 response of CHIKV-specific CD4+ T cells and the action of TGFβ likely contribute to the total IgG and IgG2c antibody deficiency and to reduced CHIKV-neutralizing titers on day 60 post-infection. The gene discussed is CD4; the disease is agammaglobulinemia.