Basic Skin Immunology

Question 1

what type(s) of immune response is the skin involved in

Answer 1

innate and adaptive immune response

Question 2

what role does the keratin layer of the skin play in immune defence

Answer 2

forms a tough, lipid rich physical barrier

Question 3

what is the keratin layer formed by

Answer 3

terminal differentiation of keratinocytes and corneocytes

Question 4

what are some of the important structural proteins in the keratin and epidermis layers of the skin

Answer 4

filaggrin, involucrin, keratin

Question 5

describe the role of keratinocytes(KC) in the epidermis

Answer 5

sense pathogens and produce; AMPs, cytokines and chemokines

Question 6

how do keratinocytes in the epidermis sense pathogens

Answer 6

via cell surface receptors, can also be activated by UV light and sensitisers(eg allergens)

Question 7

what is the function of AMPs and of cytokines and chemokines

Answer 7

AMPs = can directly kill pathogens
chemo/cytokines = recruit and regulate cells of the adaptive and innate immune response

Question 8

what is the main skin resident immune cell, and in which layer are they found

Answer 8

Langerhans cells in the epidermis

Question 9

what type of cells are Langerhans cells

Answer 9

dendritic cells/antigen presenting cells(APCs)

Question 10

what are Langerhans cells characterised by

Answer 10

the Birbeck granule

Question 11

what functions do Langerhans cells have in the skin immune response

Answer 11

they act as sentinels in the epidermis, they process lipid Ag and microbial fragments and present them to effector cells, helping activate T cells

Question 12

what layers of skin are T cells found in, and describe the levels of T cells seen in healthy skin

Answer 12

found in epidermis and dermis, healthy skin contains a large number of T cells in both layers

Question 13

what is the main type of T cell found in the epidermis and the dermis

Answer 13

epidermis = mainly CD8+ T cells
dermis = mainly CD4+ and CD8+ T cells

Question 14

where are T cells produced and sensitised

Answer 14

produced in bone marrow, sensitised in thymus

Question 15

describe the functions of CD4+ helper T cells

Answer 15

activate macrophages to destroy microorganisms, and help B cells to make antibodies

Question 16

describe the functions of CD8+ cytotoxic T cells(CTLs)

Answer 16

can kill infected cells directly, important protection against viruses and cancer

Question 17

what different types of dendritic cells(DC) are found in the dermis

Answer 17

dermal DCs and plasmacytoid DCs

Question 18

what is the role of dermal DCs

Answer 18

involved in antigen presenting and secreting cyto/chemokines

Question 19

what is the role of plasmacytoid DCs

Answer 19

produce IFN-alpha, found in diseased skin

Question 20

what other cell types in the dermis are involved in the immune response(other than DC)

Answer 20

macrophages, neutrophils and mast cells

Question 21

describe the role of mast cells in the skin immune response

Answer 21

effectors of IgE mediated immune response(allergies), binding of IgE causes mast cell activation and release of inflammatory mediators

Question 22

what can mast cells be activated by

Answer 22

IgE binding(allergy), physical trauma, certain drugs, micro-organisms

Question 23

where are MHC class I found and what is there role

Answer 23

found on almost all cells, present antigen to CD4+ T cells, present endogenous antigens

Question 24

where are MHC class II found and what is there role

Answer 24

found on APCs(eg B cells, macrophages), present to CD8+ killer T cells, present exogenous antigens