Antibodies blocking adhesion molecules such as leucocyte function anti
gen (LEA)-1 (CD11a) and intercellular adhesion molecule (ICAM)-1 (CD54
) are currently under clinical investigation for rejection prophylaxis
in organ transplantation. In a murine model a combined though not a s
ingle application of antibodies against LFA-1 and ICAM-1 can induce to
lerance towards heart transplants. No information regarding a possible
synergistic action in man is as yet available. To fill this blank we
tested the immunosuppressive capacity of ANTILFA (alpha-LFA-1) and BIR
R1 (alpha-ICAM-1) on human cells in vitro alone and in combination. Al
logeneic venous endothelial cells, the lymphoblastoid cell line MSAB o
r peripheral blood mononuclear cells were used as stimulators. DNA syn
thesis, IL-2 production and cytotoxic T cell lysis were measured to as
sess T cell response. The strongest antibody effects were seen when en
dothelial cells were used as stimulators with the T cell response bein
g assessed by IL-2 production. Most assays showed a similar immunosupp
ressive effect of LFA-1 and ICAM-1 blocking while the combination of b
oth antibodies was not significantly more effective than each antibody
alone. Thus our data do not provide a rationale for clinical trials u
sing a combination of these antibodies.