Initial characterization of cd7 deficient mice: evidence of a role for CD7 in regulation of thymocyte development
Human CD7 is a 40 kilodalton member of the immunoglobulin gene superfamily that is expressed early in natural killer and T lymphocyte development. Although CD7 involvement in lymphocyte activation has been suggested by numerous studies, the functional role of CD7 in vivo is still uncertain. To investigate roles for CD7 in lymphocyte function, we have constructed CD7 deficient (-/-) mice using homologous recombination techniques. CD7 -/- mice are viable, fertile and without apparent physical defects or clinical signs. Using immunofluorescence assays and flow cytometry, we found lymphoid populations in peripheral blood and spleen of CD7-/- mice were phenotypically normal. Examination of serum and fecal immunoglobulin levels in naive and immunized mice revealed no anomalies in total immunoglobulin levels or antigen specific antibody responses in CD7 -/- mice compared with control (+/+) littermates. However, examination of thymocyte subsets revealed a selective increase in CD4+.CD8+ double positive (DP) thymocytes with 6.7 x 10' (±8.0 xlO6) DP thymocytes in the CD7-/- mice vs 4.1 x 10' (±5.9 x 10') DP thymocytes in CD7+/+ littennates (+/- sem, n=6, p=0.027), with no significant changes in immature double negative (CD4-,CD8-) or mature CD4+ or CD8+ single positive thymocyte numbers. Thus, the phenotype of overproduction of immature DP thymocytes in CD7-/- mice provides in vivo evidence of a role for CD7 in regulation of thymopoiesis.
Lee, DM; Sundy, JS; Staats, HF; Patel, DD; Haynes, BF
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