Antigen‐specific CD8 T cells in cell cycle circulate in the blood after vaccination

• Published in: Scandinavian journal of immunology Vol. 89; no. 2; pp. e12735 - n/a
• Main Authors: Simonetti, Sonia, Natalini, Ambra, Folgori, Antonella, Capone, Stefania, Nicosia, Alfredo, Santoni, Angela, Di Rosa, Francesca
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01-02-2019; John Wiley and Sons Inc
• Subjects: Adaptive Immunity; Animals; Antigens; Antigens - immunology; antigen‐specific response; Blood; Blood Circulation; CD8 antigen; CD8-Positive T-Lymphocytes - immunology; Cell cycle; Cell Cycle - immunology; Cell Proliferation; Cell Survival; clonal expansion; Cycles; Deoxyribonucleic acid; DNA; DNA - metabolism; Experimental Immunology; Female; Flow cytometry; Flow Cytometry - methods; flow cytometry analysis; Genetic Vectors - genetics; HEK293 Cells; Humans; Ki-67 Antigen - metabolism; Lymph nodes; Lymph Nodes - immunology; Lymphocytes; Lymphocytes T; Mice; Mice, Inbred BALB C; Spleen; spleen and lymph nodes; T cells; Vaccination; viral vectors; Viruses - genetics; clonal expansion; spleen and lymph nodes; T cells; blood; antigen-specific response; flow cytometry analysis; viral vectors; vaccination
• ISSN: 0300-9475; 1365-3083
• DOI: 10.1111/sji.12735

Although clonal expansion is a hallmark of adaptive immunity, the location(s) where antigen‐responding T cells enter cell cycle and complete it have been poorly explored. This lack of knowledge stems partially from the limited experimental approaches available. By using Ki67 plus DNA staining and a novel strategy for flow cytometry analysis, we distinguished antigen‐specific CD8 T cells in G0, in G1 and in S‐G2/M phases of cell cycle after intramuscular vaccination of BALB/c mice with antigen‐expressing viral vectors. Antigen‐specific cells in S‐G2/M were present at early times after vaccination in lymph nodes (LNs), spleen and, surprisingly, also in the blood, which is an unexpected site for cycling of normal non‐leukaemic cells. Most proliferating cells had high scatter profile and were undetected by current criteria of analysis, which under‐estimated up to 6 times antigen‐specific cell frequency in LNs. Our discovery of cycling antigen‐specific CD8 T cells in the blood opens promising translational perspectives.