CD40LG and HIV infectious disease: We next examined if there was any serum antibody reactivity to HIV; specifically we did not observe any significant differences in anti-HIV p24 IgG or anti-HIV gp140 IgG between the two groups; however, IDUs had significantly higher (p<0.05) HIV gp140 IgM antibody titers (Fig 3C), which may suggest increased exposure to HIV within this population, and may reflect a history of exposure that did not result in HIV infection.