Patients with AIDS caused by HIV are highly susceptible to infection by many opportunistic pathogens including bac-teria, viruses, fungi, and parasites. This is attributed to the loss of helper T-cell activity. The virus specifically infects and kills the cells bearing CD4 surface receptors. The immu-nity is highly suppressed, and failure of immune surveil-lance leads to a high incidence of tumors.
T-cell function is altered, but immunoglobulins are normal in patients suffering from measles. Patients show a temporary suppression of delayed hypersensitivity.