- Immune cells in the epidermis are: Langerhans cells and keratinocytes- Immune cells in the dermis are: Dermal dendritic cells, lymphocytes (T cells, B cells), natural killer cells and mast cells

Epidermis:

Langerhans cells take up sentry-like positions in the epidermis, where they help cells of the immune system recognize potentially dangerous microorganisms and chemicals. They take up exogenous antigen, process it and present it to T lymphocytes either in the skin or in the local lymph nodes.Keratinocytes are the predominant cells in the epidermis. They express Toll-like receptors, which are pattern-recognition receptors that detect conserved molecules on pathogens and trigger an inflammatory response. Keratinocytes communicate with the rest of the immune system through: antimicrobial peptides, signalling cytokines, chemokines (which attract other immune cells to the epidermis), direct activation of primed T cells and NK cells

Dermis:

Dendritic cells are involved in both the innate and adaptive immune responses. During the innate response: Dendritic cells possess Toll-like receptors that can be activated by microbial components and plasmacytoid dendritic cells produce large amounts of interferon-gamma in response to viral infection.T cells are unable to recognise pathogens directly. The receptor on the surface of a T cell binds to a peptide on the surface of the APC. Effective antigen presentation allows for T cells to mature into effector T cells.B cells produce immunoglobulins that can bind to specific antigens. Antibody effector functions are: neutralisation (antibodies bind to the pathogen and prevents infection), opsonisation (the coating of the antigen surface by antibodies and the subsequent uptake by phagocytic cells)Natural killer cells are cytotoxic lymphocytes that can eliminate virally infected cells and cancer cells without antigen presentation. NK cells are activated by interferons or other cytokines released from macrophages. NOK cells express inhibitor receptors that recognise MHC-I and prevent undesirable attacks on self. They can kill target cells through the perforin-granzyme pathway.Mast cells are activated in response to allergic reactions and produce cytoplasmic granules filled with pre-formed inflammatory mediators such as histamine. They release these granules when their high-affinity immunoglobulin E receptor on the mast cell surface reacts upon contact with stimuli such as allergens, venoms, lgE antibodies and medication