This kit was based on sandwich enzyme-linked immune-sorbent assay technology. Anti- T-cell surface glycoprotein CD4 antibody was pre-coated onto 96-well plates. And the biotin conjugated anti-T-cell surface glycoprotein CD4 antibody was used as detection antibodies. The standards, test samples and biotin conjugated detection antibody were added to the wells subsequently, and wash with wash buffer. HRP-Streptavidin was added and unbound conjugates were washed away with wash buffer. TMB substrates