HETEROGENEITY OF NK AND NKT LYMPHOCYTE POPULATIONS IN HEALTHY DONORS

Abstract

Natural killer(NK) and NKT lymphocytes are important components of innate immunity, and compose a first-line defense against cancer. These populations are characterized by high heterogeneity and are divided into several subpopulations, by differences in functional activity as well as CD56 and CD16 expression. Studying heterogeneity for these lymphocyte populations in healthy donors is important, due to imbalance between different lymphocyte subsets in cancer patients. Changes in the ratio of these subpopulations may be of prognostic and clinical significance in malignant diseases. The present study was conducted with peripheral blood lymphocytes in 50 healthy donors. When analysing population of NK lymphocytes we have identified 18.0±11.3% of antigen-positive cells, their fluctuations ranged from 7.6 to 29.2%, whereas average number of cells with CD3 - CD56 + and CD3 - CD16 + phenotypes was equal to 16,2±8.1%, and 11,0±6.7%, respectively. The subpopulation analysis showed that the primary pool of NK cells was presented by CD56 dim CD16 dim cells by 52.3±19.9 percent. We detected minor subpopulations, e.g., CD56 dim CD16 bright , CD56 - CD16 + , CD56 bright CD16 - (0.3±0.2%, 1.7±0.9%, and 1.3±0.6%, respectively). Search for intracellular perforin has revealed that the number of CD56 + Perf + cells comprized 25.1±14.8%, CD16 + Perf + , 23.8±16.0%. Cytometric analysis showed that perforin is found, predominantly, in CD56 dim CD16 dim NK lymphocytes, whereas the cells with CD56 dim CD16 bright , CD56-CD16 + , CD56 bright CD16 - immunophenotypes did not produce perforin. For the first time, we have discovered a subpopulation of NK cells with the СD56dimCD16dim immunophenotype that did not contain intracellular perforin (2.0%). The NKT cell population with СD3 + CD16/СD56 + phenotype was detected in 7.1% (25% – 3.45; 75% – 8.75) antigen-positive cells, within a range of 2.5 to 11.9%. Analysis with a combination of monoclonal antibodies CD3/CD56/CD16 has shown that the number of CD3 + CD56 + cells was 4.33% (25% – 2.25; 75% – 7.3), whereas the number of CD3 + CD16 + was 3.087% (25% – 0.9; 75% – 6.2). These data demonstrate that the differences in results between the CD3/CD16/CD56, and CD3/CD16 test systems are statistically significant (p < 0.05). It was shown that the primary-pool NKT-cells are CD56 + CD16 - cells, whose number is about 5.45% (25% – 2.95; 75% – 7.3) among total CD3 + lymphocyte population. Two minor subpopulations were also detected which differed in expression of CD56 and CD16 antigens. Hence, the level of CD56 - CD16 + cells was 3% (25% – 0.25; 75% – 3.05), and the number of CD56 + CD16 + was equal to 0.67% (25% – 0.25; 75% – 0.9). Hence, the observed wide phenotypic diversity of NK and NKT-cells reflects their ability to exert various functional activities. This study, showing high heterogeneity of NK and NKT lymphocytes, may serve as a basis for the study of imbalances between different subpopulations of these cells in cancer patients.