Visualization of immune response kinetics in full allogeneic chimeras

Area of Science:

• Immunology
• Transplantation Biology
• Oncohematology

Background:

• Donor Lymphocyte Infusion (DLI) is crucial for augmenting anti-leukemia effects post-mismatched bone marrow transplantation.
• DLI efficacy correlates with donor hematopoietic cell persistence, being stronger in mixed chimeras than full chimeras (FC).
• FCs, characterized by donor antigen-presenting cells replacing host cells, exhibit reduced anti-host immunity.

Purpose of the Study:

• To evaluate changes in FC anti-host immunity using a novel in vivo cytotoxicity monitoring method.
• To assess the impact of co-transplanting donor and host hematopoietic cells on FC immune responses.

Main Methods:

• Full hematopoietic chimeras and control mice received mixtures of splenocytes labeled with CFDA-SE.
• Analysis involved fluorescence-activated cell sorting to quantify immune response based on CFDA-SE positive cells.
• NK cell depletion was performed in vivo to assess its influence on host cell rejection.

Main Results:

• FCs rejected host cells within 14 days and third-party cells within 7 days.
• NK cell depletion did not affect host cell rejection kinetics.
• Co-infusion of host-type splenocytes with naive donor-type splenocytes accelerated host cell rejection to 10 days, while naive mice rejected allogeneic cells in 3 days.

Conclusions:

• The developed method is a sensitive tool for evaluating post-transplant cytotoxicity in vivo.
• FCs demonstrate a specific deficiency in rejecting host lymphocytes, even with host antigen-presenting cells present.
• DLI enhances the anti-host immune response in FCs but does not fully restore it to naive levels.