**1. Introduction**

A better understanding of the pathogenesis of autoimmunity makes it possible to select more specific therapeutic targets and design biological agents that can replace or enhance the effect of immunosuppressive drugs; these include monoclonal antibodies, soluble receptors and molecular mimetics. This chapter aims to give a brief summary on different protein-based medications: first on the biologicals targeting cytokines that induce inflammatory responses, then on drugs depleting B cells via CD20 and CD22 and finally, on agents that inhibit cell-cell contacts and block cell survival factors. Immunogenicity of these protein preparations causes a significant problem therefore the last section gives an overview of biotechnological approaches aiming to reduce this effect.
