First Aid, Chapter 5, Anatomy, Physiology, and Pathology, Skin Flashcards
Are keratinocytes and melanocytes important in adaptive immunity?
No
What do keratinocytes express and produce that plays a role in adaptive and innate immunity?
keratinocytes do express major histocompatability complex (MHC)-type II proteins and produce several molecules (IL-1, antimicrobial peptides, thymic stromal lymphopoietin [TSLP], and receptor activator of nuclear factor κ-B ligand [RANKL]) that contribute to both the adaptive and innate immune response, respectively. These cytokines also mediate cutaneous inflammation.
What are langerhans’ cells? Where are they located? What kind of processes do they have? What happens once they are stimulated?
Langerhans’ cells are immature dendritic cells of the cutaneous immune system located in the suprabasal portion of the epidermis.
o They have dendritic processes that enable them to capture antigens entering through the skin.
o On stimulation by proinflammatory cytokines, Langerhans’ cells retract their processes, lose their adhesiveness for epidermal cells, and migrate to the dermis.
o They subsequently migrate to lymph nodes through afferent lymphatic vessels.
What percent of skin-associated lymphocytes do epidermal lymphocytes constitute? What type of lymphocytes are they mostly? How broad is the diversity of antigen receptors on these?
Epidermal lymphocytes constitute only about 2% of skin-associated lymphocytes (the rest reside in dermis), and the majority are CD8+ T lymphocytes.
o Express a more restricted set of antigen receptors than T lymphocytes in most extracutaneous tissues.
o The majority express an effector or memory phenotype.
Describe Langerhans’ cell histiocytosis. What is it caused by? What is the clinical presentation?
Langerhans’ cell histiocytosis (LCH) is a rare disease caused by clonal proliferation of Langerhans’ cells. Clinical presentation involves a nonspecific inflammatory response (fever, lethargy, weight loss) and multifocal organ involvement, including bone, skin, bone marrow, lymph nodes, endocrine glands, and lungs.
What is the function of the dermoepidermal junction?
The dermoepidermal junction joins the epidermis to the dermis. Its function is to protect against mechanical shear and to serve as a semipermeable barrier.
What are the three layers of the basement membrane?
- Lamina lucida: Includes the extracellular portion of the hemidesmosomes and anchoring filaments
- Lamina densa: Includes collagen IV and laminin network
- Sublamina densa: Includes anchoring fibrils (collagen VII)
What cells are located in the dermis?
Fibroblasts, mast cells, macrophages, dermal dendritic cells, and derma T lymphocytes.
Describe the function of fibroblasts in the dermis.
Fibroblasts synthesize and degrade extracellular matrix proteins, collagen, and elastic fibers. They also secrete soluble mediators (e.g., eotaxin when stimulated by IL-4, as well as IL-1 and IL-6).
Describe the function of mast cells in the dermis.
Mast cells have granules containing both tryptase and chymase. Their development depends on c-kit receptor and its ligand stem cell factor (SCF).
Describe the function of macrophages in the dermis.
Macrophages in dermis have several functions, including phagocytosis, antigen presentation, wound healing, and secretory functions. They express CD68.
Describe the function of dermal dendritic cells in the dermis.
Dermal dendritic cells can be labeled by factor XIIIa, and can express DCSIGN/CD 209+, CD1b, CD1c, and CD11c. They play a role in antigen presentation.
Describe the function of dermal T lymphocytes in the dermis.
Dermal T lymphocytes (both CD4+ and CD8+ cells) are located predominantly in perivascular locations. They express phenotypic markers typical of activated or memory T lymphocytes. Many dermal T lymphocytes also express a carbohydrate epitope called cutaneous lymphocyte antigen (CLA)-1, which may play a role in homing to the skin.
Where are connective tissue mast cells found? What receptor do they have?
Connective tissue mast cells with tryptase and chymase (MCTC) are present in skin, conjunctiva, heart, and intestinal submucosa (and have the CD88 receptor for C5a anaphylatoxin).
Where are mucosal mast cells found?
Mucosal mast cells with tryptase (MCT) present in the surface of the alveolar wall, the respiratory epithelium, and the small intestinal mucosa
How do some T cells home to the skin?
Skin homing of memory, effector, and regulatory T-cell subtypes (CLA+) are programmed by skin-derived dendritic cells via cytokines, such as CCR4/CCL17 and CCR10/CCL27.
What role does filaggrin play in the skin? What does mutation cause?
Filaggrin (FLG) serves as the matrix protein promoting aggregation and disulfide bonding of keratin filaments. Mutations in the FLG gene have been linked to ichthyosis vulgaris and atopic eczema. Some of these mutations have also been associated with the propensity to develop asthma in eczema patients and asthma severity that is independent of eczema.
Why should two biopsies be performed with all suspected immunobullous diseases?
In all suspected immunobullous diseases, it is best to obtain two biopsies for diagnosis. One shave biopsy of an intact vesicle or bulla for routine hematoxylin and eosin (H&E) stain; and a second biopsy of perilesional tissue for direct immunofluorescence. (Note: Immunoreactants may not be present in lesional tissue.)
