A 24-year-old recent Russian immigrant describes a long history of weight loss, night sweats and nagging cough. Imaging and biopsy of his lungs reveal numerous apical granulomas with central caseous necrosis. Surrounding the necrotic areas are large cells with abundant pale cytoplasm. Which of the following surface markers is most specific for those cells?

Question

A 24-year-old recent Russian immigrant describes a long history of weight loss, night sweats and nagging cough.  Imaging and biopsy of his lungs reveal numerous apical granulomas with central caseous necrosis.  Surrounding the necrotic areas are large cells with abundant pale cytoplasm.  Which of the following surface markers is most specific for those cells?

Quizplus · Accepted Answer

This patient's history of night sweats, weight loss, and cough with the finding of apical pulmonary granulomas showing caseous necrosis is highly suggestive of active tuberculosis. The caseating granulomas of tuberculosis consist of large epithelioid macrophages with pale pink granular cytoplasm surrounding a central region of necrotic debris. The most specific cell surface marker of the monocyte-macrophage cell lineage is CD14, which binds to bacterial lipopolysaccharide. (Choice A) Together with T cell receptors, CD4 transmembrane proteins recognize antigens presented by MHC Class II molecules. CD4 is expressed on the surface of macrophages but is also found on T helper cells. Therefore, CD4 is not a specific marker for monocytes/macrophages. (Choice B) CD7 is a multi-chain complex T cell marker. It is key to the interaction between T cells and B cells during lymphoid cell development. (Choice C) CD8 is a transmembrane protein associated with T cell receptors and found on the surface of cytotoxic T cells. Together, these proteins recognize antigenic peptides presented by MHC Class I molecules. (Choice E) CD20 is a B cell surface marker. Monoclonal antibodies against the CD-20 antigen (Rituximab) have been successful in the treatment of lymphomas. Educational Objective: The caseating granulomas of tuberculosis are almost always surrounded by large epithelioid macrophages with pale pink granular cytoplasm. CD14 is a surface marker specific to the monocyte-macrophage cell lineage.

A 24-Year-Old Recent Russian Immigrant Describes a Long History of Weight