Soluble CD8 during T cell activation.
The CD8 Ag has long been used as a surface marker for the identification of cytotoxic and suppressor cells. Recently CD8-positive cells have been shown to release a soluble form of the CD8 Ag. We have devised a sandwich monoclonal enzyme immunoassay for the quantitation of this released CD8. Soluble CD8 was released in response to lymphocyte activation. In vitro, PHA or anti-CD3 mAb-mediated T cell activation led to release of CD8 into the culture supernatant. In vivo, serum from patients with EBV-induced infectious mononucleosis (IM), a disease associated with intense CD8+ T cell activation, demonstrated elevations in soluble CD8 (7939 U/ml, day 0) compared to serum from normal controls (289 U/ml). Levels of soluble CD8 correlated (r = 0.82, p less than 0.001) with the increased percentage of CD8+/HLA-DR+ (activated CD8+ T cells) observed in acute IM. Sequential analysis of serum during the course of IM shows that soluble CD8 levels parallel the decline in CD8+/HLA-DR+ cells that occurs with the resolution of the disease. These data suggest that released CD8 may be of value in monitoring the involvement of CD8+ T cells in response to a pathologic event. The functional role of the released CD8 molecule will require further investigation.
Tomkinson
B E
BE
Department of Pediatrics, University of Massachusetts Medical School, Worcester 01655.
Brown
M C
MC
Ip
S H
SH
Carrabis
S
S
Sullivan
J L
JL
D000293:Adolescent; D000328:Adult; D000911:Antibodies, Monoclonal / Q000032:analysis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism; D002460:Cell Line; D006801:Humans; D007244:Infectious Mononucleosis / Q000276:immunology; D007700:Kinetics; D008213:Lymphocyte Activation; D013601:T-Lymphocytes / Q000276:immunology*
D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte