Interactions between cardiomyocytes and lymphocytes in tissue culture: an in vitro model of inflammatory heart disease.

Inflammation of heart tissue is a pathological feature of infections and autoimmune diseases, and sometimes also occurs after heart transplantation. In these situations, the invasive infiltration of lymphocytes, most probably cytotoxic (CD8-positive) T cells, is likely to be the cause of cardiac damage, as shown by the results of studies on experimental animal models of myocarditis. However, the cellular and molecular events underlying the interactions between lymphocytes and cardiomyocytes have hitherto not been investigated. In the present study we describe a new procedure for obtaining ventricular heart cells from neonatal mice and for maintaining them in serum-free medium in culture dishes coated with certain matrix components. Such cells adhered, spread, and were functionally active since they started a beating rhythm after 2 days. T and B cells which had been surface-labelled with biotin were added to these cells and lymphocyte adhesion was measured. The number of lymphocytes which became bound to the cardiomyocytes was calculated from the amount of biotin which remained associated with the monolayer after extensive washing to remove non-adherent cells. Colourimetric detection, using a streptavidin-peroxidase reagent, showed that an average of approximately 10 activated lymphocytes bound per heart cell, four times greater than the attachment of resting T cells. The results of this study provide a reproducible basis for using monoclonal antibodies which react against lymphocyte surface receptors and their cognate ligands to identify the specific adhesion molecules involved in heart cell recognition and interaction.