Phenotypic and functional evaluation of CD3+CD4−CD8− T cells in human CD8 immunodeficiency

• Published in: Haematologica (Roma) Vol. 96; no. 8; pp. 1195 - 1203
• Main Authors: BERNARDO, Iván, MANCEBO, Esther, GONZALEZ-SANTESTEBAN, Cecilia, PAZ-ARTAL, Estela, AGUILO, Ignacio, ANEL, Alberto, ALLENDE, Luis M, GUERRA-VALES, Juan M, RUIZ-CONTRERAS, Jesus, SERRANO, Antonio, TALAYERO, Paloma, DE LA CALLE, Oscar
• Format: Journal Article
• Language: English
• Published: Pavia Ferrata Storti Foundation 01-08-2011
• Subjects: Adolescent; Adult; Biological and medical sciences; CD8 Antigens - genetics; CD8 Antigens - metabolism; CD8-Positive T-Lymphocytes - immunology; Cytoplasm - metabolism; Cytotoxicity, Immunologic; Female; Flow Cytometry; Gene Expression Regulation - immunology; Hematologic and hematopoietic diseases; Humans; Immunodeficiencies; Immunodeficiencies. Immunoglobulinopathies; Immunopathology; Immunophenotyping; Medical sciences; Mutation - genetics; Original; Phenotype; Receptors, Antigen, T-Cell - immunology; Receptors, Antigen, T-Cell - metabolism; T-Lymphocyte Subsets - immunology; T-Lymphocyte Subsets - metabolism; Human; Cell proliferation; Immunopathology; HLA-System; Hematology; Major histocompatibility system; cytotoxic T lymphocyte proliferation; Immune deficiency; CD8 immunodeficiency; Phenotype; T-Lymphocyte; double negative T lympho cytes; Suppressive cell; Cytotoxic T lymphocyte; MHC class-I; Class I histocompatibility antigen; CD8 T lymphocyte
• ISSN: 0390-6078; 1592-8721
• DOI: 10.3324/haematol.2011.041301

Human CD8 immunodeficiency is characterized by undetectable CD8(+) lymphocytes and an increased population of CD4(-)CD8(-) (double negative) T lymphocytes.
We hypothesized that the double negative subset corresponds to the cellular population that should express CD8 and is committed to the cytotoxic T lymphocyte lineage. To assess this, we determined the phenotype and function of peripheral blood mononuclear cells and/or magnetically isolated double negative T lymphocytes from two CD8-deficient patients. To analyze the expression and co-localization with different organelles, 293T cells were transfected with plasmids bearing wild-type or mutated CD8α.
CD8α mutated protein was retained in the cytoplasm of transfected cells. The percentages of double negative cells in patients were lower than the percentages of CD8(+) T cells in healthy controls. Double negative cells mostly had an effector or effector memory phenotype whereas naïve T cells were under-represented. A low concentration of T-cell receptor excision circles together with a skewed T-cell receptor-V repertoire were observed in the double negative population. These data suggest that, in the absence of CD8 co-receptor, the thymic positive selection functions suboptimally and a limited number of mature T-cell clones would emerge from the thymus. In vitro, the double negative cells showed a mild defect in cytotoxic function and decreased proliferative capacity.
It is possible that the double negative cells are major histocompatibility complex class-I restricted T cells with cytolytic function. These results show for the first time in humans that the presence of the CD8 co-receptor is dispensable for cytotoxic ability, but that it affects the generation of thymic precursors committed to the cytotoxic T lymphocyte lineage and the proliferation of mature cytotoxic T cells.