Lecture II Flashcards
A 72-yo male comes to the physician because of a 3-wk history of blisters and severe itching that did not improve with 1% hydrocortisone therapy. Physical examination shows several 2- to 6-cm tense blisters over the abdomen, groin, and flexor surfaces of the extremities. Severe blisters appear to have ruptured, resulting in the formation of surface erosions. A skin biopsy specimen shows subepidermal, nonacantholytic blistering with a mixed eosinophilic and lymphatic perivascular infiltrate in the superficial dermis. Immunofluorescent microscopy shows a linear deposition of IgG and C3 along the basement membrane. Which of the following epithelial structures most likely contains the antigen associated with the disease process? A. Adherens junction (zonula adherens) B. Desmosome (macula adherens) C. Gap junction D. Hemidesmosome E. Tight junction (zonula occludens)
D. Hemidesmosome Bullous pemphigoid (seen in this scenario) is mediated by autoantibodies that react with components of hemidesmosomes, disrupting the connection of epithelial cells to the underlying tissue and resulting in bulla formation. The immune mechanism of this condition can be regard-ed as a type II hypersensitivity reactions. Pemphigus vulgaris is mediated by autoantibodies that react with desmosomes, disrupting cell-cell connections in mucosa and skin. It starts with small vesicles, usually on the oral or nasal mucosa, and then spreads to other parts of the body. Bullae are delicate and flaccid. Nikolsky’s sign (production of blistering by light stroking or rubbing of the skin) is positive. Pemphigus is most common from ages 40 to 60.
In the small intestine, proteins localized in the basolateral surface of epithelial cells are prevented from migrating to the apical surface of the cell by the presence of which of the following labeled structures in the diagram?
A. Tight junctions (zonulae occludentes)
Blood is drawn from a 34-year-old male with bacterial meningitis for a complete blood count. The leukocyte count is elevated. Which of the following is released by the predominant type of white blood cell present?
A. Histamine
B. Leukotrienes
C. Lysozyme
D. Peroxidase
E. Vasoactive amines
C. Lysozyme
This question requires you to know that bacterial infections are associated with an elevated neutrophil count. These leukocytes represent ~60% of all leukocytes, have 3-5 nuclear lobes, and are filled with granules that contain bactericidal products, including lysozyme. Had the infection been viral, there would have been an increase in lymphocytes instead.
Histamine (choice A) is released by basophils and mast cells, along with other vasoactive amines (choice E). The “slow-reacting substance of anaphylaxis” (which consists of leukotrienes LTC4, LTD4, and LTE4 (choice B)) is also released by basophils, which possess large, dark blue/black spheroidal granules. Basophils and mast cells are basophilic (thus their name) and metachromatic, because of the presence of heparin, a glycosaminoglycan.
Eosinophils contain peroxidase (choice D). These white blood cells have a bilobed nucleus and possess red acidophilic granules in their cytoplasm. They also contain hydrolytic enzymes. Note that an increased eosinophil count is associated with parasitic infections, allergies, asthma, and some neoplasms.
physical/mechanical barrier, chemical agents and normal flora are all
components of the skin immunity
keratinocytes
closely connected cells of the skin cross-linked with keratin, high turnover rate and prevents evaporation
the skins chemical agents
ph, and antimicrobial agents (cathelicidins, defensins, and dermicidins)
landergans cells
derived from bone marrow, dendritic cells located among keratinocytes, function as antigen presenting cells in immune responses to contact antigens and some skin gradts; contain birbeck granules
birbeck granula- unique to the skin and unknwon function
top arrow is pointing to the __________ and bottom arrow is pointing to the ______
langerhans cells and cytoplasmic process
langerhans cell
mucosa
epithelium, lamina propria (loose connective tissue with glands), and muscularis mucosae (smooth muscle)
submucosa
dense irregular connective tissue
muscularis externa
inner smooth muscle and outer smooth muscle
external layer
adventitia (loose CT) and serosa (loos CT)
- tight junction
- zonula adherens
- desmosome
H- hemidesmosome
tight junction
an occludens junction, composed of claudins and occludins (proteins); prevents leaking between cells and precents movement of membrane proteins
zonula adherens
an adherens junction, composed of cadherins, binds to actin of the terminal web (cytoskeleton)
desmosome
an adherens juntion, composed of desmoplakins and plakoglobins
gap junctions
a communicatin junction, composed of connexins
hemidesomosome
an adherns junction, connects the cell to the basement membrane so it is not an intracellular junction
IgA
resistant to proteolytic enzymes, so it can coexist with proteases in gut lumen
antigens in the gut are bound by ______ and undergo transcytosis into the intraepithelial pockets
M cells
__________ cells take up the antigen process it, and present it to the helper T lymphocytes
dendritic
_______ are then stimulated to differentiate into plasma cells which secrete IgA antibodies
B lymphocytes
