INTRODUCTION:

Anti-CD40L monoclonal antibody (MR1) treatment, blocks the CD40-CD40L costimulatory rejection pathway, and has been shown to increase survival of murine cardiac allotransplants. Previous work in our laboratory has demonstrated the effectiveness of MR1 in dramatically reducing the Th1 and Th2 responses to peripheral nerve allografts. This study sought to investigate the effect of a 3 day course of MR1 inductive therapy on functional muscle recovery following peripheral nerve allografting.

METHODS:

A two-by-two design was used to investigate the effects of MR1 therapy versus vehicle on murine peripheral nerve isografts (C57BL/6 into C57BL/6) and allografts (BALB/c into C57BL/6), with six animals per group. 0.8 cm grafts were harvested from the left peroneal nerve, extending from just distal to its division from the sciatic to just proximal to its division into the superficial and deep branches. Grafts were transplanted into similar 0.8 cm defects in the recipients, utilizing 2-3 stitch coaptations with 11-0 nylon. On days 0, 1 and 2, each recipient received an IP injection of either MR1 (1.0 mg in 0.2 ml saline) or vehicle alone. All mice convalesced for 60 days following nerve grafting. The extensor digitorum longus (EDL) muscle was then harvested, maximum tetanic isometric force was measured in-vitro, the muscle was weighed, and the muscles and peroneal nerves were preserved for histomorphometric analysis.

RESULTS:

Sixty days following peroneal nerve grafting, mean P_o for EDL muscles in the vehicle treated allograft group was 16% lower than the mean for animals in the MR1 treated allograft group. Two way analysis of variance showed a significant effect for the variable of graft type (isograft vs. allograft), but not for treatment type (with or without MR1).

Maximum tetanic force (P_o, in mN):

	Isograft	Allograft
Vehicle	230 ± 32	175 ± 30
MR1	228 ± 19	209 ± 42

(Values are reported as means ± S.D.)

CONCLUSIONS:

Short-term MR1 inductive therapy appears to hold promise for reducing or eliminating peripheral allograft rejection through blockade of the CD40-CD40L costimulatory pathway. In this experiment, a difference in mean values of 19% between P_o for MR1 treated and untreated allografts was observed but was not significant. This lack of significance can possibly be explained as a result of small sample sizes, or may be related to the model and the time point chosen. Efforts are currently underway to increase animal numbers in each experimental group.