Novel cross-reactive anti-idiotype antibodies with properties close to the human intravenous immunoglobulin (IVIg).

The most important link between the immune network theory and clinically useful therapies so far is the use of human intravenous immunoglobulin (IVIg) in the treatment of autoimmune diseases. Although still controversial, one of the main mechanisms that has been postulated for the in vivo effects of IVIg, is the selection of immune repertoires through idiotypic interactions. We describe here anti-idiotype IgG monoclonal antibodies (MAbs), which were obtained by immunization of syngeneic mice (Balb/c) with an anti-ganglioside antibody. These anti-idiotype MAbs show multiple idiotypic connections and share some of the properties of the IVIg pool. The antiidiotype (Ab2) MAbs B7 and 34B7 showed heterogeneous binding with the idiotypes of several anti-ganglioside antibodies, MAbs obtained from splenocytes of nonimmunized newborn mice, F(ab')2 fragments of IgG human myeloma proteins, and nonimmunoglobulin antigens. The recognition pattern of the B7 MAb to the idiotypes of human immunoglobulins was also studied using a phage display library obtained from the variable region genes of an asymptomatic AIDS patient and also F(ab')2 fragments obtained from an IVIg pool of healthy human donors. We also demonstrated that these MAbs produced some of the in vitro effects reported for the human IVIg pool, such as the inhibition of cell proliferation of human B and T cell lines and of normal human lymphocytes activated with different mitogens. Another striking property of the MAb B7 was its ability to induce a dose-dependent specific antibody T-cell response in vivo in syngeneic mice. Both anti-idiotype MAbs showed anti-metastatic effect in vivo when injected intravenously to mice inoculated with MB16-F10 melanoma cells. The antimetastatic effect of the antiidiotype MAbs was not observed in athymic mice inoculated with the same tumor. This kind of antibody can become an interesting tool for further exploration of the role of idiotypic network connections in the regulation of the immune system and to study the effects of interventions on network connectivity in experimental autoimmune disease, using a reagent better chemically defined than the IVIg pool.