Major histocompatibility complex class I and class II expression by myocytes in cardiac biopsies posttransplantation.

A total of 85 cardiac biopsies from patients 23-265 days posttransplant were studied for the correlation of the rejection grade score with the level of major histocompatibility complex (MHC) class I and class II expression on cardiac myocytes and endothelial cells, the quantitative level of leukocytic infiltrate, and the immunophenotype of the leukocytes. Results indicate a lack of absolute correlation between rejection grade scores and levels of MHC antigen expression. Further, a lack of absolute correlation was also seen with quantitation of leukocytic infiltrates and relative levels of MHC antigen expression. Of great interest was our preliminary finding that as early as 4 weeks prior to a rejection episode scored by routine histological criteria as grade 4, cardiac biopsy from the patient demonstrated high levels of MHC class I and class II expression. Similar increases of MHC antigen expression prior to an increase in histological rejection score grades were also noted in serial biopsies of 2 other patients. These data suggest that it may be quite useful to examine levels of MHC antigens on cardiac biopsies posttransplantation as an additional parameter for monitoring of cardiac rejection episodes.

Interferon-gamma-treated K562 target cells distinguish functional NK cells from lymphokine-activated killer (LAK) cells.

In vitro incubation of the erythroleukemic cell line K562 with interferon-gamma (IFN-gamma) renders these cells relatively resistant to natural killer (NK) cell lysis. However, such treatment does not alter their sensitivity to LAK cell lysis. Thus, the lytic susceptibility of interferon-gamma-treated K562 (I-K562) cells to LAK cells as opposed to its relative resistance to NK cell lysis provides a functional assay to help distinguish these two types of effector cells. The relative resistance of I-K562 for NK cell-mediated lysis was not secondary to the release of soluble factors or the frequency of Leu-19+, CD3+ T cells, residual IFN-gamma, or expression of MHC Class I molecules. Coincubation of I-K562 cells with NK or LAK cells overnight did not appreciably change the pattern of lytic responses against K562 and I-K562 target cells. However, incubation of PBMC in vitro with I-K562 but not native K562 in the presence of r-IL-2 leads to a marked decrease in the generation of LAK cells. The inhibition of LAK cell generation was not secondary to differences in the consumption of bioactive levels of IL-2. Differences in the lytic capability of NK and LAK effector cells suggest heterogeneity among cells that mediate such non-MHC-restricted lysis. Use was made of cells from a patient with a large granular lymphocyte lymphoproliferative disease (greater than 85% Leu-19+) to determine if such cells could be used to distinguish clonal population of cells which would represent NK or LAK cell function. Of interest was the finding that such cells, even after incubation in vitro with IL-2, showed lytic function representative of NK cells but not LAK cells. Data concerning the inhibition of LAK cell generation by I-K562 cells have important implications for future therapeutic trials of IFN-gamma and IL-2 in the treatment of human malignancies.

Characterization of human cardiac infiltrating cells post transplantation. 1. Phenotypic and functional alloreactivity.

Sequential cardiac biopsies from patients post transplantation were studied for histological evidence of grades of rejection, the immunophenotype of the mononuclear cell infiltrate if present and, in addition, aliquots of the same biopsy were cultured in vitro with medium containing interleukin-2. The exuding mononuclear cells were expanded and bulk cultures and T cell lines resulting from this were evaluated phenotypically and functionally for donor specific alloreactivity. Results of these studies demonstrate: (1) No strict correlation of histological rejection grades with immunophenotype or degree of mononuclear cell infiltrate. (2) The mononuclear cell cultured from 102 biopsies yielded 47 relatively pure CD4+ T cell cultures and 12 cultures enriched for CD4+ T cells, 16 relatively pure CD8+ T cell cultures and 15 cultures enriched for CD8+ T cells, 7 cultures which consisted of dual marked CD4+ CD8+ T cells and 5 which were negative for both CD4 and CD8 but expressed CD3. (3) Of the 59 total CD4+ T cells, 6 demonstrated donor specific CTL reactivity and of the 31 CD8+ T cells, 26 demonstrated donor specific CTL activity. (4) None of the CD4+ CD8+ T cell cultures demonstrated CTL reactivity and all 5 of the CD3+ CD4- CD8- T cell cultures demonstrated potent donor specific CTL activity. (5) Of the 102 cultures, 89 showed donor specific PLT function. (6) High MHC-Class I expression by cardiac myocytes correlated with high frequency of CTL cultures. These data provide a summary of the phenotype and functional analysis of T cells in cardiac biopsy specimens and provide valuable reagents for further studies on the mechanisms involved in human cardiac allograft rejection.