The investigation of the impact of -550 (H/L) and -221 (X/Y) mutations located in the promoter region of the MBL gene on CD4+ T lymphocytes and HIV-1 plasma viral load suggested that haplotypes related to medium and low levels of MBL protein in serum might have an important influence on the progression of HIV-1 infection [67]. The gene discussed is CD4; the disease is HIV-1 infection.