Secreted Molecules

Secreted molecules are molecules that are actively moved by organisms from within a cell to the space outside of the cell. These secreted substances are usually functional proteins, although they can be a diverse range of non-protein products, such as steroids. Cellular signaling requires the interaction of secreted molecules. Cytokines are secreted proteins that are essential to the immune response. Interleukins are released cytokines that promote development and differentiation of T and B lymphocytes and hematopoietic cells.