Background: The role of B cells and macrophages in microvascular disease after heart transplantation remains controversial.
Methods: Out of a total of 809 endomyocardial biopsies without evidence of acute cellular rejection (n = 422, 72 females and 350 males, median age 46 years), 393 without evidence of the quilty phenomenon were investigated zero to ten years after heart transplantation. Vascular reaction (endothelial cell swelling and vessel wall thickening) was graded by H&E staining, and immunohistochemistry was performed for T cells (clone UCHL1), B cells (clone L26) and macrophages (clone KP1) and evaluated semi-quantitatively (light microscopy x 200).
Results: Positive reaction for T cells and macrophages as well as evidence of endothelial cell swelling decreased with time after heart transplantation. Positive reactions for B cells were less frequent and increased slightly during the observation time, while vessel wall thickening dominated the last observation interval between the fourth and tenth years. Severity of vascular reaction was independent of immunohistochemical evidence of B cells or macrophages.
Conclusions: While activation of the humoral and the non-specific immunological system is common after heart transplantation, microvascular alterations seem to develop independently of these findings.