The aim of immunological treatment of infections and tumors is to enhance immune responsiveness via the use of thymic hormones (thymopoietin, pen-tapeptides), leukocyte extracts, or interferons. Derivatives or synthetic analogs of microorganisms such as BCG, components of Corynebacteriumparvum and peptidoglycans (e.g., muramyl peptide), or oligonucleic acids (CpG), are used as adjuvants. Components of streptococci and Streptomyces, eluates and fractions of bacterial mixtures, and the related synthetic substance levami-sole are also used. The role of Toll-like receptors in these adjuvant effects is becoming increasingly understood, with a major role of these molecules being to link non-specific innate resistance to specific immunity. .

Recently developed immune therapy strategies aim to improve antigen presentation. For instance interleukins, or costimulatory molecules such as B7 or CD40, have been inserted into tumor cells by means of transfection. Hybrid antibodies have been constructed in an attempt to improve antigen recognition and phagocytosis (one such example is the coupling of an anti-CD3 antibody with tumor antigen-specific antibodies). Other ideas tested successfully in model experiments include systemic treatment with interleu-kins (this presents with frequent toxicity problems) or targeted insertion of GM-CSF, TNF, or IL-2. Alternatively, the production of IFNy or IFNb by cells, or the use of molecules capable of polyclonal T- and B-cell stimulation has been employed. This concept utilizes local chronic or acute infections with the aim of achieving inflammation surrounding, or direct infection of, tumor cells resulting in their cytolytic destruction. Such concepts have also been used to force phagocytosis and uptake of antigens by APCs with the aim of inducing or enhancing tumor immunity (e.g., BCG infections in bladder carcinoma treatment).

Kayser, Medical Microbiology © 2005 Thieme

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Essentials of Human Physiology

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