Purification of natural human IFN-gamma antibodies

Natural and therapeutically-induced antibodies to cytokines

Serum samples obtained from non-immunocompromised patients treated therapeutically with recombinant cytokines (e.g. Il-1alpha; Il-1beta; Il-2 to Il-18; IFNalpha; GM-CSF; G-CSF; etc.) often reveal the presence of high affinity anti-cytokine antibodies. Antibody Fab binding in a saturable manner by ELISA and RIA or western immunoblotting prove their specificity. Antibody level often increases in these patients with repeated cytokine administration, suggesting boosts of antigen stimulation. However, the appearance in circulation of auto-antibodies to exogenous cytokine is not always associated with a decreased clinical response to therapy. The demonstration that non-neutralizing auto-antibodies to several natural cytokines can be found even in sera of normal healthy individuals never treated before with cytokines and particularly during the last trimester of pregnancy and in cord-blood, suggests that these naturally- occurring and therapeutically-induced auto-antibodies may exert different functions, not only as inhibitors or antagonists but also as beneficial physiological cytokine carriers or regulators of their activity.

Natural antibodies to interferon-gamma

Natural antibodies to interferon (IFN)-gamma were detected in the serum of virus-infected patients and also, at a low titre, in the serum of healthy subjects. The increased titre of antibodies to IFN-gamma in the sera of virus-infected patients, and its decrease with clinical resolution, indicate that these antibodies are related to viral infection and probably reflect IFN-gamma production as a result of antigenic stimulation in vivo. Natural antibodies to IFN-gamma were affinity purified and studied for their capability to interfere in vitro with the multiple activities of the lymphokine. Data obtained show that these human anti-IFN-gamma antibodies have no inhibitory effect on the antiviral and antiproliferative activity of IFN-gamma and do not interfere with the binding of the lymphokine to its specific cell receptor. Instead, they can inhibit the expression of HLA-DR antigens induced by IFN-gamma on U937 cells and interfere, in mixed lymphocyte culture, with the proliferation of lymphocytes and the generation of cytotoxic lymphocytes. Experiments in animal models suggest that natural antibodies to IFN-gamma may have a role in the immunoregulatory process limiting the intensity and/or duration of immune response. As they can interfere only with the immunomodulating activities of IFN-gamma, these antibodies might open up new therapeutic approaches to diseases with evidence of activated cell-mediated immunity.

Down-regulation of cytokine action

The study of cytokines that regulate all areas of cellular communication has expanded over the past few years. The control and modulation of the complex network of cytokine action remains an area of intense interest. Agents that will modulate cytokine signal transduction at the cellular level will assist in the understanding of the molecular basis of cytokine cellular activation and in the design of drugs for the management of clinical disease. Recent work has demonstrated the existence of complex mechanisms of negative regulation of cytokine action. New methods utilizing isolated protein products that participate in immunomodulation may prove useful for clinical regulation of the host response to cytokine up-regulation. Currently, most interest in soluble cytokine receptors, natural cytokine inhibitors, genetically engineered cytokine antagonists and single or combinations of anti-inflammatory cytokines has focused on the possibility that they may become standard pharmacological agents for the treatment of inflammatory complications of clinical disease. Specifically, TNF and IL-1 inhibitors and the cytokines IL-10 and TGF-beta, alone or in combination may be effective for the inhibition of severe clinical inflammation. Soluble receptors for other cytokines such as IL-6 may prove to be carrier proteins that enhance cytokine action and will require cautious investigation. Because most cytokines are pleiomorphic in their activities, down-regulation through the utilization of direct inhibitors or anti-inflammatory cytokines may cause immunosuppression, making the host susceptible to opportunistic infection. Selective and short-term inhibition of inflammatory cytokine action may be necessary to prevent unwanted clinical side-effects.