Melanism - Immune System

Immune System

Melanin has several physiological roles in maintaining health, such as the synthesis of vitamin D. Melanin is the primary determinant of the degree of skin pigmentation and protects the body from harmful ultraviolet radiation. Synthesis of 1,25-dihydroxyvitamin D₃ in the skin, however, is dependent on ultraviolet B light. Highly pigmented skin, to the level found in people of African origin, abrogates almost all ultraviolet-induced 1,25-(OH)₂D₃ synthesis. Numerous animal models and clinical studies have underlined the essential role of vitamin D as a modulator of the different processes of the immune system. Evidence indicates that serum concentrations of 1,25-(OH)₂D₃ and the prevalence of autoimmune diseases in a certain population are associated with the latitude at which that population resides.

Genes for melanism in felines may provide resistance to viral infections. A viral epidemic may explain the prevalence of black leopards in Java and Malaysia, and the relatively high incidence of black leopards and black servals in the Aberdares region of Africa. Previously, black furred felines in the Aberdares had been considered a high altitude adaptation since black fur absorbs more heat.

Studies reported in New Scientist magazine in 2003 also suggested that recessive-gene melanism is linked to disease resistance rather than altitude. Melanistic cats may have better resistance to disease than cats with "normal" color coats. This would explain why recessive melanism persists when melanistic individuals are disadvantaged because they are poorly camouflaged in open areas.