Skin Immunology Flashcards
Terminal differentiation of ? to ? forms the keratin layer
Of keratinocytes to corneocytes
What is the keratin layer also known as?
Stratum corneum
How do keratinocytes contribute to the immune function of skin?
- Sense pathogens via cell surface receptors and help mediate an immune response.
- Produce antimicrobial peptides (AMPs) that can directly kill pathogens (AMPs have been found at high levels in skin of patients with psoriasis)
- Produce cytokines and chemokines.
What characterises Langerhans cells?
Birbeck granules
What is the main immune cell of the skin and what do they do?
Langerhans cells - they are dendritic antigen presenting cells which process antigens and present them to effector T cells
Which kind of T cells are mainly found in the epidermis?
CD8+ T cells
Which kind of T cells are mainly found in the dermis?
CD4 + and CD8+
Interaction between which two things is involved in antigen recognition and T cell activation?
T cell receptor (TCR) and the Major Histocompatibility Complex (MHC)
Which co-receptors enhance the interaction between TCR and MHC in antigen recognition and T cell activation?
CD4+ helper T cells and CD8+ cytotoxic T cells
Which 2 types of dendritic cells are found in the dermis?
Dermal dendritic cells (antigen presenting and secrete city/chemokine) and plasmacytoid dendritic cells (pDC) - produce INFalpha as an alarm
Which cells are MHC class I and MHC class II found?
Class I - on almost all cells and Class II- antigen presenting cells (eg. B cells, macrophages)
What is the role of MHC?
Control the immune response through recognition of ‘self’ and ‘non-self’.
Which cells mediate psoriasis?
T cell mediated
What is the hallmark of skin lesions in psoriasis?
Inflammation
What is the pathophysiology of psoriasis?
Psoriasis is a hyperproliferative disorder, involving a complex cascade of inflammatory mediators. Keratinocytes are stimulated so mitotic activity of basal and suprabasal cells is significantly increased, with cells migrating from the basal layer to the stratum corneum in just a few days - this forms the scaly layer of corneocytes
What is the pathogenesis of atopic eczema?
Impairment of the skin barrier due to decreased AMP in skin and mutation in the fillagrin gene leads to the dry skin, as fillagrin is nature’s own moisturiser. Impairment of the skin’s barrier function leads to an increased sensitisation to cutaneous antigens
What are the 2 types of immunodeficiency?
Primary (genetic) and secondary (acquired)
What mediates Type I (Immediate) Hypersensitivity responses?
Antibody mediated - IgE
What mediates Type II and Type III Hypersensitivity responses?
Antibody mediated - IgG and IgM
What is the pathogenesis of Type I hypersensitivity reactions?
Early exposure to allergen causes the production of IgE, which binds to FcεR1 receptor on mast cells. Later exposure causes rapid crosslinking of the receptors, signal transduction and degranulation of the mast cell.
Which type of hypersensitivity reaction is an allergic reaction?
Type I
What mediates Type IV (delayed) hypersensitivity reactions?
Cell mediated: Th1 cells
What kind of reactions are Type II hypersensitivity reactions?
Cytotoxic reactions
What kind of reactions are Type III hypersensitivity reactions?
Immune complex-mediated reactions
