nary epithelium. Moreover, soluble proteins and small bioactive molecules such as complement proteins, defensins and ficolins 1-3, pro-inflammatory cytokines, chemokines, lipid mediators of inflammation, membrane-bound receptors and cytoplasmic proteins are part of the innate immune system. Both innate and adaptive immunity is mediated by leukocytes. Lymphocytes circulate between the blood system and the lymphatic system, passing through the peripheral lymphoid organs, which includes the sp