St. Yoon et al., BOTH HIGH AND LOW AVIDITY ANTIBODIES TO THE T-CELL RECEPTOR CAN HAVE AGONIST OR ANTAGONIST ACTIVITY, Immunity, 1(7), 1994, pp. 563-569
Anti-TCR antibodies can activate or block the activation of T cells. I
n the present experiments, we have shown that different monoclonal ant
ibodies to the same TCR can have either agonist or antagonist activity
, and we have examined the relationship between these functional effec
ts and the avidity of the antibody for the TCR. We show here that it i
s not the avidity of an anti-TCR antibody that determines whether it a
cts as an agonist or an antagonist. Moreover, we show that monovalent
Fab fragments of agonist antibodies produce detectable changes in T ce
ll behavior. These data suggest that T cell activation may involve not
just aggregation of the TCR but also some induced change in individua
l ligated receptors, and that agonists may produce this change while a
ntagonists do not. We argue that similar effects may apply to peptide-
MHC ligands as well.