Antimicrobial peptides (AMPs), as a part of innate immune system of ticks and other living organisms, are able to eliminate pathogens. In ticks the most important group of AMPs is defensin family. In this work, defensin from the tick D. marginatus was studied. The defensin gene was isolated from D. marginatus fed females. Using RT-PCR the gene expression was detected in salivary glands and mitgut. Recombinant protein was expressed in the procaryotic expression system, purified and tested for its antimicrobial activity. Specific polyclonal rabbit antibodies (anti DR IgG) were prepared and tested for their specifity and sensitivity.