CD8+ alpha beta+ T cells that lack surface CD5 antigen expression are a major lymphotactin (XCL1) source in peripheral blood lymphocytes.
To better characterize the cellular source of lymphotactin (XCL1), we compared XCL1 expression in different lymphocyte subsets by real-time PCR. XCL1 was constitutively expressed in both PBMC and CD4(+) cells, but its expression was almost 2 log higher in CD8(+) cells. In vitro activation was associated with a substantial increase in XCL1 expression in both PBMC and CD8(+) cells, but not in CD4(+) lymphocytes. The preferential expression of XCL1 in CD8(+) cells was confirmed by measuring XCL1 production in culture supernatants, and a good correlation was found between figures obtained by real-time PCR and XCL1 contents. XCL1 expression was mostly confined to a CD3(+)CD8(+) subset not expressing CD5, where XCL1 expression equaled that shown by gammadelta(+) T cells. Compared with the CD5(+) counterpart, CD3(+)CD8(+)CD5(-) cells, which did not express CD5 following in vitro activation, showed preferential expression of the alphaalpha form of CD8 and a lower expression of molecules associated with a noncommitted/naive phenotype, such as CD62L. CD3(+)CD8(+)CD5(-) cells also expressed higher levels of the XCL1 receptor; in addition, although not differing from CD3(+)CD8(+)CD5(+) cells in terms of the expression of most alpha- and beta-chemokines, they showed higher expression of CCL3/macrophage inflammatory protein-1alpha. These data show that TCR alphabeta-expressing lymphocytes that lack CD5 expression are a major XCL1 source, and that the contribution to its synthesis by different TCR alphabeta-expressing T cell subsets, namely CD4(+) lymphocytes, is negligible. In addition, they point to the CD3(+)CD8(+)CD5(-) population as a particular T cell subset within the CD8(+) compartment, whose functional properties deserve further attention.
Department of Oncology and Surgical Sciences, University of Padova, Padova, Italy.
Laura
L
Stievano
Valeria
V
Tosello
Novella
N
Marcato
Antonio
A
Rosato
Annalisa
A
Sebelin
Luigi
L
Chieco-Bianchi
Alberto
A
Amadori
D000328:Adult; D017252:CD3 Complex / Q000096:biosynthesis; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D018956:CD5 Antigens / Q000378:metabolism; D016827:CD8 Antigens / Q000096:biosynthesis*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism*; D002478:Cells, Cultured; D054360:Chemokine CXCL1; D019744:Chemokines, C / Q000096:biosynthesis* / Q000097:blood; D019742:Chemokines, CC / Q000096:biosynthesis; D019743:Chemokines, CXC / Q000096:biosynthesis; D002648:Child; D002675:Child, Preschool; D006801:Humans; D016130:Immunophenotyping; D036341:Intercellular Signaling Peptides and Proteins; D007700:Kinetics; D016131:Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism*; D008222:Lymphokines / Q000096:biosynthesis* / Q000097:blood; D008875:Middle Aged; D012795:Sialoglycoproteins / Q000096:biosynthesis* / Q000097:blood; D016176:T-Lymphocyte Subsets / Q000276:immunology / Q000378:metabolism
D017252:CD3 Complex; D018956:CD5 Antigens; D016827:CD8 Antigens; C431698:CD8alpha antigen; C433839:CD8alphabeta antigen; C477867:CD8beta antigen; C475829:CXCL1 protein, human; D054360:Chemokine CXCL1; D019744:Chemokines, C; D019742:Chemokines, CC; D019743:Chemokines, CXC; D036341:Intercellular Signaling Peptides and Proteins; D008222:Lymphokines; D012795:Sialoglycoproteins; C092390:XCL1 protein, human; C018997:lymphotactin