Alveolar macrophage populations are distorted in immunocompromised patients with pneumonitis

Abstract

Alveolar macrophages (AM) were obtained by bronchoalveolar lavage (BAL) from patients presenting with pneumonitis: 30 human immunodeficiency virus (HIV)-infected individuals and 12 transplant recipients. Nine normal volunteers acted as controls. The cells were washed and cytospins prepared. Monoclonal antibodies (MoAbs) and immunoperoxidase methods were used to analyse the expression of HLA-DR molecules as well as phenotypic macrophage markers. P values apply to the differences between medians using the Mann-Whitney test. Median percentages of macrophages, lymphocytes and neutrophils were similar in all three groups. No differences were found in the median percentages of macrophages expressing the monocyte phenotype (MoAb UCHM1, CD14). However, in HIV-infected patients and transplant recipients a median of only 45% of macrophages expressed the pan-macrophage phenotype identified by MoAb EBM11 (CD68) in contrast with 98% in the normal volunteers. The AM population expressing the dendritic cell marker (MoAb RFD1) was also markedly reduced in both groups of immunocompromised patients (2 vs 28% in normal volunteers). Transplant recipients had significantly more phagocytic cells identified by MoAb RFD7 than the HIV-infected patients (25 vs 2%), but the numbers were still low when compared with the volunteers (48%). HLA-DR expression on BAL cells was reduced by 90% in both immunocompromised groups. For the transplant recipients, severity of pneumonitis was correlated with expression of dendritic cell marker RFD1, (Spearman's rank correlation r = 0.538, p less than 0.05) and pan-macrophage marker EBM11 (r = 0.581, p less than 0.05), while no such correlation was found in HIV-infected patients. These results suggest that a defective macrophage population is probably a serious factor contributing to immunosuppression.

Abnormal alveolar macrophage populations in bone marrow transplant recipients with pneumonitis

“…BRAY er al. [20] also found reduced DR expression on alveolar rnacrophages in patients with the acquired immune deficiency syndrome (AIDS). Reduced ability of MLC to present antigen in the lung could be responsible for increased susceptibility to opportunistic pulmonary infections.…”

“…Some of these results differ from those of BRAY er al. [20], but this earlier study included a mixture of cases with solid organ transplants, where patients had also received different pretransplant conditioning. Furthermore, unlike the present study, 50% of the transplant recipients reported by BRAY er al.…”

“…Furthermore, unlike the present study, 50% of the transplant recipients reported by BRAY er al. (20] were smokers.…”

The phenotype of alveolar macrophages and its correlation with immune cells in bronchoalveolar lavage

“…In contrast to many adhesive molecules which are expressed on both monocytes (the precursors of AMs in the peripheral blood) and macrophages, molecules such as CD71 (receptor for transferrin), KiM8, and 25F9 are found preferentially on mature tissue macrophages, including AMs Distinct phenotypic subpopulations of AMs have recently been identified [15,16]. Macrophages with properties of dendritic, phagocytic or suppressive cells may be separated on the basis of the eo-expression of membrane antigens RFD1, RFD7 and RFD9 [17,18].…”