8-31 IMM Host Barriers Flashcards
Desmosomes vs Hemidesmosomes
Desmosomes attach keratinocytes to adjacent cells while hemidesmosomes attach keratinocytes to the basal lamina/basement membrane
Physical/mechanical barrier of the skin
- Closely connected cells (keratinocytes) with cross-linked keratin
- High turn over rate
- Prevents evaporation
pH of the skin (acidic or basic)
acidic
What are Langerhans cells?
Dendritic cells located among keratinocytes derived from bone marrow that function as antigen presenting cells in immune responses to contact antigens. Also contain Burbeck granules
What are goblet cells?
Wine glass shaped cell that secretes mucus onto epithelial cells for lubrication and protection - like a unicellular gland
What makes up the mucosa?
- Epithelium
- Lamina propia (loose connective tissue with glands)
- Muscularis mucosae (smooth muscle)
5 intercellular junctions
1) Tight junction
2) Zonula adherens
3) Desmosome
4) Gap junction
5) Hemidesmosome
What is a tight junction?
- composed of occludins and claudins (proteins)
- prevents leaking between cells and the movement of membrane proteins
What are zonula adherens?
- an adherens junction composed of cadherins
- binds to actin of the terminal web (cytoskeleton)
What is a desmosome?
- an adherens junction composed of desmoplakins and plakoglobins
What are gap junctions?
- a communicating junction made of connexions
What are hemidesmosomes?
- an adherens junction that connects the cell to the basement membrane
Antimicrobial factors in the small intestine
Lysozyme from Paneth cells
Mucosal immunity in the intestine
1) antigens in the gut lumen are bound by M cells (microfold) and undergo transcytosis into their intraepithelial pockets
2) dendritic cells take up antigen, process it and present it to helper T lymphoctyes
3) B lymphocytes are then stimulated to differentiate into plasma cells which secrete IgA antibodies
4) IgA is transported into gut lumen where it binds to antigen receptors on surface of microorganisms neutralizing potentially harmful invaders before they can enter mucosa
Oral cavity epithelium
- cells slough off to prevent biofilm production
- contains langerhans cells and intraepithelial lymphocytes
Oral cavity lamina propria
- contains macrophages
- contains dendritic cells that project “dendrites” into the epithelium to uptake antigens to secondary lymphoid tissue
Components of saliva
- lysozyme - breaks bacterial cell walls
- lactoferrin - binds iron to deprive microbes of nutrients
- histatins - prevents candida and strep growth
- salivary IgA - aggregates bacteria
What is pemphigus vulgaris?
- formation of intraepidermal bullae starting in oral cavity and going to skin
- autoimmune attack of desmosomes and can be fatal
What is bullous pemphigoid?
- subepidermal bullae
- autoimmune attack of hemidesmosomes and much less severe
Respiratory tract mucus clearance is aided by…
- coordinated secretion of mucins and proteins
- sufficient water for hydration
- beating cilia
- sneezing and coughing (sometimes)
Antimicrobial factors of the respiratory tract
- antioxidants
- defensins
- lactoferrins
- lysozymes
Vaginal method of host barrier
- epithelium secretes glycogen that good bacteria turn to lactic acid creating an acidic environment unfavorable to pathogenic microorganisms
Tamm-Horsfall protein
- from kidney and binds bacteria preventing it from attaching to urinary tract lining
Eye glands (3)
- lacrimal gland: tears
- meibomian glands: sebaceous glands on eyelid
- ciliary glands: apocrine sweat glands on eyelid
