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Macrophages, multinucleated giant cells, and apoptosis in HIV+ patients and normal blood donors
B Ruibal-Ares1, N E Riera, M M de Bracco
1Instituto de Investigaciones Hematologicas, Academia Nacional de Medicina, Buenos Aires, Argentina.
Abstract:
Clearance of apoptotic debris is carried out by cells of the monocyte/macrophage lineage and, as other macrophage functions, it can be altered in AIDS, leading to the accumulation of apoptotic cells observed in this disease. In this study we evaluated the ability of macrophages from human immunodeficiency virus (HIV)-infected patients to differentiate and to clear apoptotic debris in prolonged in vitro cultures. Peripheral blood mononuclear cells (PBMC) from infected hemophilia patients were cultured in the absence of exogenously added stimulators and the organization and morphological characteristics of the cultures were analyzed and correlated with clinical staging of the patients. Cell aggregates of different sizes involving macrophages and lymphocytes were formed in cultures from asymptomatic HIV+ patients (CDC groups II-III) and controls and in 4/7 group IV C2 HIV+ patients. In order to obtain viable and organized cultures, cells had to be handled carefully, allowing contact and undisturbed sedimentation in round-bottom tubes. Multinucleated giant cells (MGC) were formed through macrophage fusion after 5 days of culture in HIV- controls, group II and III patients, and some of the group IV C2 patients, while scarce formation of MGC was observed in AIDS patients or patients with advanced HIV disease. This paucity was correlated with impaired dead cell removal and accumulation of apoptotic debris. Viability of macrophages and MGC was reduced after 15 days. MGC and the macrophages (either free or in cell aggregates) were able to remove dead cells, clearing the cultures of cell debris. Furthermore, in group II and III HIV+ hemophilic patients, increased macrophage-MGC phagocytic activity, suggesting in vivo activation, was frequently observed. In HIV+ patients with AIDS or advanced HIV disease (CDC groups IV A, IV C1, and IV D) dead cell removal was impaired and apoptotic debris accumulated. Long-term cultures of unstimulated PBMC are an interesting model for studying the role of macrophages and/or MGC in the removal of dead cells as well as examining the cellular milieu in which HIV replicates in an individual host.
Insights
Macrophages from HIV-infected patients show impaired ability to clear apoptotic debris, especially in advanced disease stages. This dysfunction contributes to cell accumulation and may indicate altered immune cell activity in human immunodeficiency virus (HIV) infection.
Area of Science:
- Immunology
- Cell Biology
- Virology
Background:
- Clearance of apoptotic debris is a critical macrophage function.
- This function can be impaired in acquired immunodeficiency syndrome (AIDS).
- Accumulation of apoptotic cells is a hallmark of AIDS.
Purpose of the Study:
- To evaluate the differentiation and apoptotic debris clearance capacity of macrophages from human immunodeficiency virus (HIV)-infected patients.
- To analyze macrophage and multinucleated giant cell (MGC) formation and function in vitro.
- To correlate these functions with clinical staging of HIV infection.
Main Methods:
- Long-term in vitro culture of peripheral blood mononuclear cells (PBMC) from HIV-infected and control individuals.
- Analysis of cell organization, morphology, and multinucleated giant cell (MGC) formation.
- Assessment of apoptotic debris clearance and phagocytic activity.
Main Results:
- Cell aggregates and MGCs formed in cultures from asymptomatic HIV+ patients and controls.
- Scarce MGC formation and impaired dead cell removal were observed in AIDS patients.
- Increased phagocytic activity was noted in early-stage HIV+ patients, suggesting in vivo activation.
- Apoptotic debris accumulated in cultures from patients with advanced HIV disease.
Conclusions:
- Macrophage differentiation and apoptotic debris clearance are impaired in advanced HIV disease.
- Paucity of MGC formation correlates with reduced dead cell removal.
- Long-term PBMC cultures serve as a model to study macrophage function and the HIV cellular milieu.