Th1/Th2 cytokine profile of the immune response in limb component transplantation

Background: The purpose of this study was to define the cytokine secretion pattern during limb allograft rejection and to determine its correlation to differential tissue antigenicity of limb allograft components. Methods: Twenty-five C57B1/6 mice (H-2K(b)) were randomized to six groups. The experimental groups were recipients of vascularized Balb/c mice (H-2K(d)) allografts consisting of skin, muscle, whole limb, or limb with the skin removed or nonvascularized nerve allografts. The unmodified rejection response was studied by histology, flow cytometry, and ELISPOT assay to quantify IFN-gamma (Th1) and IL-4 (Th2) production. Results: The greatest Th1 response was seen in the recipients of allografts composed of skin (973.3 +/- 93 spots/million spleen cells; mean +/- SEM), followed by whole limb (961.3 +/- 86/million), nerve (613.3 +/- 245/million), limb with skin removed (483 +/- 246/million), and then muscle (460 +/- 234/million). Recipients of skin, whole limb, and nerve allografts had the highest IFN-gamma:ILr4 ratios, or greatest Th1 deviation, of 3.1 +/- 0.4, 3.0 +/- 0.2, and 2.9 +/- 0.6, respectively. These were significantly greater than those that received muscle (0.9 +/- 0.3) and limb allografts with skin removed (1.0 +/- 0.4) (p<0.05). Conclusions: The skin component produced the greatest Th1 activation of the immune response and appears to be a critical component of the overall antigenicity of the whole limb allograft, as evidenced by the Th2 shift seen when the skin was removed. Muscle produced the least Th1 differentiation, with nerve being intermediate.