Immunohistochemical profile of mononuclear infiltrate in the myocardium of transplanted heart. Computer morphometry data

Aim. To carry out a quantitative immunophenotypic characterisation of cellular corporations in a mononuclear inflammatory myocardial infiltrate in the cell and humoral forms of heart transplant rejection using the computer morphometry of endomyocardial biopsy samples.

Materials and methods. Endomyocardial biopsy samples (n = 226) were obtained from 56 heart recipients who underwent transplantation in 2018–2019. Sections with a thickness of 5 μm after the paraffin infiltration were stained with hematoxylin and eosin according to the standard procedure. The expression of CD3 T-lymphocyte, CD20 B-lymphocyte and CD68 macrophage markers was determined by the immunohistochemical streptavidin-biotin method. Using computer morphometry, the staining area coefficient (SAC) was calculated as the percentage of the total area of the stained objects to the area of the biopsy. The statistical processing of the results included verification of the distribution nature by the Kolmogorov-Smirnov method and the calculation of the Cramer — Welch criterion.

Results. Lymphocytes and macrophages were found in the inflammatory infiltrate of all heart transplants. The expression of CD3 T-lymphocyte marker in the absence of rejection (0R) was at SAC = 0.99 ± 0.02%. In comparison with 0R cases, this coefficient increased 2.1 times (p <0.05), 3.4 times (p <0.05), 5.5 times (p <0.05) and 4.8 times (p <0.05) in 1R, 2R, 3R and humoral rejection, respectively. The expression of the CD20 B-lymphocyte marker in 0R cases was characterised by SAC = 0.19 ± 0.01%. In comparison with 0R cases, this coefficient increased 2.7 times (p <0.05), 3.4 times (p < 0.05), 4.4 times (p <0.05) and 9.5 times (p <0.05) in 1R, 2R, 3R and humoral rejection, respectively. The value of the CD68-positive macrophage region for 0R was only 0.34 ± 0.01%. This parameter increased 2.7 times (p <0.05), 4.0 times (p <0.05), 9.6 times (p <0.05) and 4.1 times (p <0.05) in 1R, 2R, 3R and humoral rejection, respectively.

Conclusion. Cellular corporations in the mononuclear inflammatory infiltrate of transplanted heart are characterised by the predominance of T-lymphocytes in the cases of both cellular and humoral rejection. The expression of the B-lymphocyte marker is most pronounced in an antibody-mediated form. The maximum presence of macrophages in the infiltrate characterises severe cell rejection. An increase in the severity of cell rejection leads to an increase in the relative content of B-lymphocytes and macrophages in the infiltrate.