Impact of CXCR4/CXCL12 Blockade on Normal Plasma Cells In Vivo

Area of Science:

• Immunology
• Hematology
• Pharmacology

Background:

• Plasma cells (PCs) are crucial for alloantibody production in transplant recipients and exhibit resistance to current therapies.
• Stromal microenvironments influence normal PC localization, development, and survival through receptor-ligand interactions.
• CXCR4/CXCL12 signaling is implicated in PC homing and retention within specific niches.

Purpose of the Study:

• To investigate the role of CXCR4/CXCL12 interactions in PC retention and sensitivity to bortezomib.
• To determine if plerixafor, a CXCR4 antagonist, can deplete PCs or sensitize them to proteasome inhibitor therapy.

Main Methods:

• Mice were treated with plerixafor at various doses to assess PC mobilization and distribution.
• CXCR4 expression was analyzed on PCs in spleen, bone marrow, and peripheral blood.
• Bortezomib was administered alone and in combination with plerixafor to evaluate synergistic effects on PC depletion.

Main Results:

• Plerixafor treatment led to significant mobilization of PCs from the spleen into peripheral blood, an effect abrogated by splenectomy.
• The total number of PCs in the spleen and bone marrow remained unchanged after plerixafor administration.
• Bortezomib reduced PC numbers, but the addition of plerixafor did not enhance this cytotoxic effect.

Conclusions:

• CXCR4/CXCL12 interactions are vital for retaining a specific subpopulation of PCs within the spleen.
• Plerixafor-mediated CXCR4/CXCL12 blockade does not deplete PCs nor improve bortezomib efficacy.
• PC resistance to bortezomib is likely mediated by factors independent of CXCR4/CXCL12 interactions.