Cloning the rat homolog of the CD28/CTLA-4-ligand B7-1: structural and functional analysis.
T cell activation involves the delivery of two independent signals to the naive T cell. The first signal occurs with engagement of the TCR. One of the best characterized second signals is ligation of CD28 on the surface of T cells by B7 molecules (B7-1, B7-2) present on the surface of activated antigen presenting cells (APCs). Recent studies have demonstrated that injection of a human fusion protein, CTLA-4-Ig, which in humans binds to both B7-1 and B7-2, prevents cardiac allograft rejection in a rat transplantation model when given 48 h after engraftment. In order to better characterize the role of B7-1 (which is maximally expressed 48 h after activation of APCs) in this model, as well as in models of tumor-induced immune responses, we have cloned the rat homolog of B7-1, and now report on its structure and function. A 1030 bp cDNA containing the entire coding sequence of the rat B7-1 was cloned with a polymerase chain reaction strategy utilizing degenerate primers derived from published murine and human B7-1 sequences. The rat B7-1 coding sequence is 67 and 81% homologous to human and murine B7-1 cDNAs, and the predicted peptide sequence is likewise 57 and 66% identical to the peptide sequences of human and murine B7-1 respectively. The greatest area of identity occurs in the extracellular portion of the molecule, particularly the Ig-C like domain.(ABSTRACT TRUNCATED AT 250 WORDS)
Judge
T A
TA
Department of Internal Medicine, University of Michigan Medical School, Ann Arbor 48109, USA.
Liu
M
M
Christensen
P J
PJ
Fak
J J
JJ
Turka
L A
LA
D000595:Amino Acid Sequence; D000818:Animals; D018122:B7-1 Antigen / Q000235:genetics* / Q000276:immunology*; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D002478:Cells, Cultured; D003001:Cloning, Molecular / Q000379:methods*; D008213:Lymphocyte Activation / Q000276:immunology; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D051381:Rats; D011914:Rats, Inbred BN; D012260:Ribonucleases / Q000032:analysis; D013601:T-Lymphocytes / Q000276:immunology; D014162:Transfection / Q000235:genetics
D018122:B7-1 Antigen; D012260:Ribonucleases