Both IgA subclasses are reduced in parotid saliva from patients with AIDS.

Secretory IgA (SIgA), the isotypes IgA1 and IgA2, and IgM were measured by ELISA in stimulated parotid saliva from patients with AIDS (n = 16), subjects with asymptomatic HIV infection (n = 28), and HIV-seronegative healthy controls (n = 19). SIgA was significantly reduced in the AIDS group (10.4 micrograms/ml) compared with the asymptomatic HIV-infected subjects (17.1 micrograms/ml) and the controls (23.0 micrograms/ml). This decrease comprised both IgA1 and IgA2 to a similar extent on a relative basis. The SIgA decrease in AIDS patients was in striking contrast to their serum IgA level, which was significantly increased (6.9 g/l) compared with the asymptomatic HIV-infected subjects (2.9 g/l) as well as the controls (2.8 g/l). Low parotid output of SIgA in patients with HIV infection was associated with low numbers of CD4+ lymphocytes in peripheral blood as well as the presence of oral infections. The parotid output of IgM was similar in all groups. A low level of SIgA in the external secretions of patients with AIDS may well contribute to their frequent mucosal infections of opportunistic microorganisms.