Endothelial cell receptors on leukemic plasma cells

Area of Science:

• Immunology
• Hematology
• Cell Biology

Background:

• Lymphocyte recirculation is mediated by specific cell surface receptors that enable homing to lymphoid tissues.
• Plasma cell leukemia and multiple myeloma are malignant plasma cell disorders characterized by neoplastic B-cell proliferation.

Purpose of the Study:

• To investigate the in vitro binding of neoplastic plasma cells to high endothelial venules (HEVs).
• To determine if leukemic plasma cells retain the ability to interact with HEVs, a feature typically lost in terminally differentiated B cells.

Main Methods:

• In vitro binding assays using peripheral blood mononuclear cells from plasma cell leukemia patients and bone marrow mononuclear cells from multiple myeloma patients.
• Incubation of patient cells with rat lymph node HEVs.
• Detection of monoclonal cytoplasmic immunoglobulins to confirm neoplastic origin.

Main Results:

• Peripheral blood mononuclear cells from plasma cell leukemia patients showed selective adherence to HEVs.
• Bone marrow mononuclear cells from multiple myeloma patients exhibited variable binding to HEVs; in some cases, adherence was observed but the cells lacked plasmacytoid features.
• Neoplastic plasma cells demonstrated the presence of endothelium-recognizing structures, which is unusual for terminally differentiated B cells.

Conclusions:

• Leukemic plasma cells in plasma cell leukemia possess functional endothelium-recognizing structures, enabling binding to HEVs.
• This finding is significant as terminally differentiated B cells typically lose such receptors, suggesting unique characteristics of leukemic plasma cells in maintaining or acquiring these structures.