8-31 IMM Host Barriers

Question 1

Desmosomes vs Hemidesmosomes

Answer 1

Desmosomes attach keratinocytes to adjacent cells while hemidesmosomes attach keratinocytes to the basal lamina/basement membrane

Question 2

Physical/mechanical barrier of the skin

Answer 2

• Closely connected cells (keratinocytes) with cross-linked keratin
• High turn over rate
• Prevents evaporation

Question 3

pH of the skin (acidic or basic)

Answer 3

acidic

Question 4

What are Langerhans cells?

Answer 4

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

Question 5

What are goblet cells?

Answer 5

Wine glass shaped cell that secretes mucus onto epithelial cells for lubrication and protection - like a unicellular gland

Question 6

What makes up the mucosa?

Answer 6

• Epithelium
• Lamina propia (loose connective tissue with glands)
• Muscularis mucosae (smooth muscle)

Question 7

5 intercellular junctions

Answer 7

1) Tight junction
2) Zonula adherens
3) Desmosome
4) Gap junction
5) Hemidesmosome

Question 8

What is a tight junction?

Answer 8

• composed of occludins and claudins (proteins)

- prevents leaking between cells and the movement of membrane proteins

Question 9

What are zonula adherens?

Answer 9

• an adherens junction composed of cadherins

- binds to actin of the terminal web (cytoskeleton)

Question 10

What is a desmosome?

Answer 10

• an adherens junction composed of desmoplakins and plakoglobins

Question 11

What are gap junctions?

Answer 11

• a communicating junction made of connexions

Question 12

What are hemidesmosomes?

Answer 12

• an adherens junction that connects the cell to the basement membrane

Question 13

Antimicrobial factors in the small intestine

Answer 13

Lysozyme from Paneth cells

Question 14

Mucosal immunity in the intestine

Answer 14

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

Question 15

Oral cavity epithelium

Answer 15

• cells slough off to prevent biofilm production

- contains langerhans cells and intraepithelial lymphocytes

Question 16

Oral cavity lamina propria

Answer 16

• contains macrophages

- contains dendritic cells that project “dendrites” into the epithelium to uptake antigens to secondary lymphoid tissue

Question 17

Components of saliva

Answer 17

• lysozyme - breaks bacterial cell walls
• lactoferrin - binds iron to deprive microbes of nutrients
• histatins - prevents candida and strep growth
• salivary IgA - aggregates bacteria

Question 18

What is pemphigus vulgaris?

Answer 18

• formation of intraepidermal bullae starting in oral cavity and going to skin
• autoimmune attack of desmosomes and can be fatal

Question 19

What is bullous pemphigoid?

Answer 19

• subepidermal bullae

- autoimmune attack of hemidesmosomes and much less severe

Question 20

Respiratory tract mucus clearance is aided by…

Answer 20

• coordinated secretion of mucins and proteins
• sufficient water for hydration
• beating cilia
• sneezing and coughing (sometimes)

Question 21

Antimicrobial factors of the respiratory tract

Answer 21

• antioxidants
• defensins
• lactoferrins
• lysozymes

Question 22

Vaginal method of host barrier

Answer 22

• epithelium secretes glycogen that good bacteria turn to lactic acid creating an acidic environment unfavorable to pathogenic microorganisms

Question 23

Tamm-Horsfall protein

Answer 23

• from kidney and binds bacteria preventing it from attaching to urinary tract lining

Question 24

Eye glands (3)

Answer 24

• lacrimal gland: tears
• meibomian glands: sebaceous glands on eyelid
• ciliary glands: apocrine sweat glands on eyelid