The Influence of Cytomegalovirus on Expression of HLA‐G and its Ligand KIR2DL4 by Human Peripheral Blood Leucocyte Subsets

• Published in: Scandinavian journal of immunology Vol. 86; no. 5; pp. 396 - 407
• Main Authors: Albayati, Z., Alyami, A., Alomar, S., Middleton, D., Bonnett, L., Aleem, S., Flanagan, B. F., Christmas, S. E.
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.11.2017
• Subjects: Adult; Antibodies, Viral - blood; Antigens; Antigens, Viral - administration & dosage; CD4 antigen; CD56 antigen; CD69 antigen; CD8 antigen; Cell culture; Cell Proliferation; Cytomegalovirus; Cytomegalovirus - immunology; Cytomegalovirus - pathogenicity; Cytomegalovirus Infections - genetics; Cytomegalovirus Infections - immunology; Female; Gene expression; Histocompatibility antigen HLA; HLA-G Antigens - genetics; HLA-G Antigens - metabolism; Humans; Immune Evasion; Immunosuppression; In Vitro Techniques; Interleukin 2; Killer cell immunoglobulin-like receptors; Killer Cells, Natural - immunology; Killer Cells, Natural - virology; KIR2DL4 protein; Leukocytes; Leukocytes - classification; Leukocytes - immunology; Leukocytes - virology; Ligands; Lymphocytes; Lymphocytes B; Lymphocytes T; Male; Middle Aged; Mixed culture; Peripheral blood; Polymerase chain reaction; Potassium channels (inwardly-rectifying); Pregnancy; Receptors, KIR2DL4 - genetics; Receptors, KIR2DL4 - metabolism; RNA, Messenger - genetics; RNA, Messenger - metabolism; Serum levels; T-Lymphocyte Subsets - immunology; T-Lymphocyte Subsets - virology; Young Adult
• ISSN: 0300-9475; 1365-3083; 1365-3083
• DOI: 10.1111/sji.12594

HLA‐G is a non‐classical class I HLA antigen, normally expressed in high levels only on extravillous cytotrophoblast. It has immunosuppressive properties in pregnancy and has also been found to be upregulated on leucocytes in viral infection. In this study, proportions of all leucocyte subsets expressing HLA‐G were found to be low in healthy subjects positive or negative for cytomegalovirus (CMV). Significantly greater proportions of CD4+ CD69+ and CD56+ T cells expressed HLA‐G compared to other T cells. However, following stimulation with CMV antigens or intact CMV, proportions of CD4+, CD8+, CD69+ and CD56+ T cells, and also B cells expressing HLA‐G, were significantly increased in CMV+ subjects. Despite some subjects having alleles of HLA‐G associated with high levels of expression, no relationship was found between HLA‐G genotype and expression levels. Purified B cells from CMV+ subjects stimulated in mixed culture with CMV antigens showed significantly increased HLA‐G mRNA expression by real‐time polymerase chain reaction. Serum levels of soluble HLA‐G were similar in CMV− and CMV+ subjects but levels in culture supernatants were significantly higher in cells from CMV+ than from CMV− subjects stimulated with CMV antigens. The HLA‐G ligand KIR2DL4 was mainly expressed on NK cells and CD56+ T cells with no differences between CMV+ and CMV− subjects. Following stimulation with IL‐2, an increase in the proportion of CD56+ T cells positive for KIR2DL4 was found, together with a significant decrease in CD56dimCD16+ NK cells. The results show that CMV influences HLA‐G expression in healthy subjects and may contribute to viral immune evasion.