What effect do IL-4 and IL-13 have on cathelicidin expression in the skin?

Interleukin-4 (IL-4) and interleukin-13 (IL-13) are cytokines that play significant roles in the immune response, particularly in the context of allergic reactions and inflammation. In the skin, these cytokines are known to downregulate the expression of cathelicidin, which is a part of the innate immune system and has antimicrobial properties.

The mechanism involves the signaling pathways activated by IL-4 and IL-13, which are primarily associated with T-helper 2 (Th2) immune responses. When these cytokines are present, they promote a shift toward a Th2-dominant immune environment, which can lead to the suppression of various components of innate immunity, including cathelicidin.

By inhibiting cathelicidin expression, IL-4 and IL-13 can contribute to the susceptibility to infections and may play a role in the pathogenesis of skin conditions such as atopic dermatitis. Therefore, the effect of IL-4 and IL-13 on cathelicidin expression in the skin is one of inhibition.