Subclinical GvHD in non-irradiated F1 hybrids: severe lymphoid-tissue GvHD causing prolonged immune dysfunction

Area of Science:

• Immunology
• Transplantation Biology
• Hematology

Background:

• Graft-versus-host disease (GvHD) is a major complication following allogeneic hematopoietic stem cell transplantation (SCT).
• Parent-in-F1 hybrid models are commonly employed to investigate GvHD immunobiology.
• Existing parent-in-F1 models exhibit variable GvHD characteristics based on strain and induction methods.

Purpose of the Study:

• To investigate a previously undescribed pattern of parent-in-F1 T-cell alloreactivity.
• To characterize the effects of serial parental splenocyte infusions on recipient tissues.
• To understand the immunobiology of a novel GvHD presentation.

Main Methods:

• Utilized non-irradiated B6DBA2F1 and B6SJLF1 mice as recipients.
• Administered high-dose C57BL/6 splenocytes via weekly infusions.
• Monitored clinical health, donor T-cell chimerism, and tissue pathology.
• Assessed hematopoiesis, lymphoid tissue composition, and antigen-presenting cell (APC) function.

Main Results:

• High-dose splenocyte challenge resulted in high-grade donor T-cell chimerism with minimal clinical signs of GvHD in most recipients.
• A minority of recipients developed bone marrow failure-type GvHD or graft rejection.
• Long-term F1 chimeras exhibited prolonged pancytopenia, severe lymphopenia, and impaired APC function.
• Hematopoiesis and lymphoid tissues recovered only after multilineage donor chimerism was established.

Conclusions:

• Reported a novel type of parent-in-F1 hybrid GvHD induced by cumulative high-dose parental splenocytes.
• This subclinical GvHD primarily affects hematolymphoid tissues, leading to prolonged immune incompetence.
• Findings highlight the complexity of GvHD in parent-in-F1 models and its impact on immune recovery.