Human stem cell colony-stimulating activity (CFU-GEMMCSA) in medium conditioned by leukemic B-lymphocytes

Area of Science:

• Hematology
• Immunology
• Cell Biology

Background:

• Chronic lymphocytic leukemia (B-CLL) involves abnormal B-lymphocyte proliferation.
• The role of B-lymphocytes in regulating normal hematopoiesis is not fully understood.

Purpose of the Study:

• To investigate the effect of B-CLL B-lymphocytes on hematopoietic stem and progenitor cell growth.
• To determine if B-cell activation influences the production of colony-stimulating factors.

Main Methods:

• Culturing B-lymphocytes from B-CLL patients.
• Assessing conditioned media for colony-stimulating activity on human marrow cells (CFU-GEMM, GM-CFU, BFU-E).
• Stimulating B-lymphocytes with mitogens (Staphylococcus aureus Cowan strain, anti-mu) and measuring 3H-thymidine uptake.

Main Results:

• B-CLL B-lymphocyte conditioned media induced multilineage (CFU-GEMM), granulocyte-macrophage (GM-CFU), and erythroid (BFU-E) colony formation.
• Maximum stem cell colony-stimulating activity (CFU-GEMMCSA) was observed by day 3.
• Mitogen stimulation (SAC, anti-mu) enhanced CFU-GEMMCSA production, independent of DNA synthesis.

Conclusions:

• B-lymphocytes, even in the context of B-CLL, produce factors that stimulate hematopoietic stem and progenitor cell growth in vitro.
• B-cell activation can enhance the production of these hematopoietic growth factors.
• These findings suggest a regulatory role for B-lymphocytes in hematopoiesis.