Behaviorally conditioned suppression of a graft-versus-host response

Area of Science:

• Immunology
• Pharmacology

Background:

• Cyclophosphamide (CY) is known to condition suppression of humoral immune responses.
• The potential for CY to condition suppression of graft-versus-host response (GvHR) was unexplored.

Purpose of the Study:

• To investigate if conditioned immunosuppression, induced by cyclophosphamide, can suppress graft-versus-host responses (GvHR).

Main Methods:

• Female (Lewis x Brown Norway) F1 rats were conditioned by pairing saccharin solution consumption with a single low-dose intraperitoneal injection of CY (50 mg/kg) 48 days before immunization.
• Animals received splenic leukocytes from Lewis donors to induce GvHR.
• Regional GvHR was assessed by measuring popliteal lymph node weights on day 5.

Main Results:

• Conditioned rats re-exposed to the conditioned stimulus showed significantly lower lymph node weights compared to controls.
• The immunosuppressive effect in conditioned animals was comparable to those receiving three CY injections during the GvHR.
• This indicates conditioned immunosuppression affects cellular immune responses like GvHR.

Conclusions:

• Conditioned immunosuppression can effectively suppress graft-versus-host responses.
• The findings extend the understanding of conditioned immunosuppression to cellular immune responses, beyond previously studied humoral responses.