Progression of HIV disease is associated with increased expression of Fc gammaRI and CR1 on alveolar macrophages

The expression of receptors for complement and the Fc region of immunoglobulin by alveolar macrophages (AM) constitutes a valuable aid to effector function of these cells. However, during HIV infection such expression may also act to increase binding of immune complexes, thus facilitating viral infection of these cells. This study was designed to determine whether changes in the expression of these receptors occurs in situ during HIV infection. Lung macrophages were isolated by bronchoalveolar lavage in groups of HIV+ subjects segregated on the basis of peripheral CD4 count. A group of normal subjects was also investigated. Expression of CR1 and Fc gammaRI was quantified by measuring the optical density of reaction product following controlled immunoperoxidase staining with MoAbs CD35 and CD64. Both CR1 and Fc gammaRI were increased over normal in all HIV+ subjects. This increase was progressive with advancing disease as determined by correlation with declining peripheral CD4 count. Comparison of asymptomatic and symptomatic subjects with HIV infection showed no difference in CR1 expression but a rise in Fc gammaRI expression in the latter group. An overall inverse correlation was also found between peripheral CD4 count and Fc gammaRI expression, but not CR1 expression. These data demonstrate a significant increase in the expression of these receptors on AM from HIV+ subjects, and show that this increase may occur before any symptoms in these patients.