Effects on human and nonhuman primate immune response of a new rat anti-CD2 monoclonal antibody.
BACKGROUND
Nonhuman primate models are highly clinically relevant in transplantation. The development of immunosuppressive tools or a tolerogenic regimen for primate models therefore represents an important goal of transplantation immunological research. Hence, we have developed a rat monoclonal antibody (mAb) that recognizes the CD2 molecule (LO-CD2b) on both human and nonhuman primate cells.


METHODS
The LO-CD2b mAb has been characterized by flow cytometry, E-rosetting inhibition, and Western blotting. In vitro inhibition of immune responses by LO-CD2b was assessed after both mitogenic and allogeneic stimulation in mixed lymphocyte reactions (MLR). Several LO-CD2b dose and time responses were tested. In vivo, peripheral and lymph node T-cell depletion was examined both by flow cytometry and immunohistology in 10 baboons that received intravenous injection of LO-CD2b at different doses and time courses. Xenosensitization (anti-rat) was assessed by ELISA. Renal allograft survival was followed in two baboons treated with iterative LO-CD2b injections.


RESULTS
In vitro, LO-CD2b binds a lymphocyte antigenic determinant of 52 kDa that is recognized by other well-characterized anti-CD2 mAbs (T11, Leu5b). LO-CD2b recognized natural killer CD2+ cells. Administration of 200 ng/ml LO-CD2b almost completely inhibited human and baboon mitogenic stimulation. Allogeneic baboon and human MLR were completely inhibited by the addition of LO-CD2b (at 312 ng/ml) on the day of the initiation of culture; when added after 1 or 2 days, LO-CD2b still provided a significant MLR inhibition (>50%). Incubation of LO-CD2b with baboon peripheral blood mononuclear cells produced very low cytokine levels (interferon-y, tumor necrosis factor-alpha, interleukin 2). In secondary MLR, baboon peripheral blood mononuclear cells previously incubated with LO-CD2b were unable to respond to a second allogeneic stimulation but were able to react to mitogens. In vivo, within the first hour after LO-CD2b injection (at 0.15, 0.5, and 2 mg/kg), an 85-90% peripheral depletion of CD2+ cells was observed. A partial T-cell depletion in inguinal lymph nodes was seen after 1 week. The mechanism of peripheral T-cell depletion could have been antibody-dependent cell cytotoxicity or opsonization but was complement independent. Iterative LO-CD2b injections (12 days at 0.35 mg/kg) slightly prolonged the renal allograft survival in two baboons.


CONCLUSIONS
LO-CD2b is a nonactivating rat anti-CD2 mAb able to strongly inhibit both mitogenic and allogeneic responses in human and nonhuman primates. In vivo, LO-CD2b provides a rapid peripheral T-cell depletion, which is reversible within days after the cessation of injections. This rat mAb represents a very important tool for in vivo experimental investigation in nonhuman primates because it similarly reacts against human T cells in vitro.
Laboratory of Experimental Surgery, Université catholique de Louvain, Brussels, Belgium.
J P
JP
Dehoux
S
S
Talpe
N
N
Dewolf
M
M
Otsuka
F
F
Oike
F
F
Jamar
B
B
de la Parra
D
D
Latinne
H
H
Bazin
P
P
Gianello
D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000097:blood; D000911:Antibodies, Monoclonal / Q000097:blood / Q000276:immunology*; D018801:CD2 Antigens / Q000276:immunology*; D016207:Cytokines / Q000096:biosynthesis; D005260:Female; D006085:Graft Survival; D006801:Humans; D016130:Immunophenotyping; D007205:Indium Radioisotopes; D007668:Kidney / Q000473:pathology; D016030:Kidney Transplantation / Q000276:immunology; D008198:Lymph Nodes / Q000276:immunology / Q000473:pathology; D008213:Lymphocyte Activation; D008212:Lymphocyte Depletion; D008297:Male; D010215:Papio; D051381:Rats; D014184:Transplantation, Homologous
D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; D018801:CD2 Antigens; D016207:Cytokines; D007205:Indium Radioisotopes