More interestingly, when co-culturing B cells with autologous CD4+ T cells from moderate-to-severe SLE patients highly expressing ICAM-1, the blockade of ICAM-1 also induced increased IgG production whereas no increase was observed from mild SLE with low-expression of ICAM-1 on CD4+ T cells. Here, CD4 is linked to systemic lupus erythematosus.