**14. Immunomodulatory activity**

Besides the beneficial properties of cyanobacteria, their immunomodulatory activity exhibits diverse effects on immune systems, such as the increase of phagocytic activity in macrophages, the stimulation of antibody and cytokine production and the accumulation of natural killer cells into tissues, or the activation of T and B cells [134]. For instance, the effect of *Spirulina* in mice was investigated by Hayashi et al., who demonstrated increased phagocytic activity and antigen production. Enhanced phagocytic and natural killer cell-mediated antitumor activities, together with increased antigen production, were also shown in chicken by Qureshi and Ali [29]. Additionally, the incremental impact of cyanobacteria extracts on 13.6-fold interferon and 3-fold interleukin (IL)-1b and -4 was observed in human blood cells. Despite *Spirulina* has been proved to be safe, other cyanobacteria (e.g., *Microcystis sp*.) produce metabolites that are cytotoxic to lymphocytes and have inhibitory effects on membrane-bound leucine amino peptidase, which is related to antigen-processing and antigen presentation response [47, 135], confirmed the immune-toxicity of microcystin that presented medical competence in the lipopolysaccharide-induced lymph proliferation in mice vaccinated with sheep T-dependent antigen red blood cells.
