Expression of tumor necrosis factor in human acute cardiac rejection: An immunohistochemical and immunoblotting study

The authors performed an immunohistochemical study on expression of tumor necrosis factor alpha (TNFα) in endomyocardial biopsies from human cardiac allografts. TNFα immunoreactivity was found in 45% biopsies with mild acute rejection, in 83% biopsies with focal moderate rejection, in 80% biopsies with diffuse moderate rejection. Biopsies with absent rejection did not show immunoreactive cells. In mild rejection, positive cells were few and scanty monocytes and macrophages (MAC-387 and LN5 positive cells) and T lymphocytes (UCHL-1/CD45 RO positive cells) (up to 20% of all infiltrating cells). Expression of major histocompatibility complex (MHC) class II antigens on infiltrating and endothelial cells occurred earlier and independent of TNFα reactivity. Number of immunoreactive cells increased in moderate rejection (up to 50%). Immunoreactivity was also present in nonpigmented macrophages in part of the biopsies with resolving rejection (45%). The authors conclude that TNFα is expressed in acute cardiac rejection by immunologically activated inflammatory cells. Immunoreactive cells increase in number with increasing severity of the reaction.