Immunology Flashcards
Skin provides a barrier and front line defence between us and what?
Pathogens, chemical insults and physical trauma
Factors that contribute to the skin as an immunological system
Structure
Cell types
Cytokines, chemokines, eicosanoids and antimicrobial peptides
Genetics
How does the structure of the skin contribute to the skin as an immunological system?
Has a keratin layer and stratification
Function of cytokines
Proteins which encourage migration between cells
Function of chemokines
Attract migration of cells
What happens to an infection in a normal immune response?
It is controlled
Hypersensitivity
Overreaction to antigen
Immunodeficiency - is the infection controlled?
Infection not controlled and tumours may arise
Autoimmunity
Reaction to host tissue causing chronic inflammation
Stratum corneum
Keratin layer - formed by terminal differentiation of keratinocytes to corneocytes
Important structural proteins in the stratum corneum
Fillagrin, involucrin, keratin
Functions of keratin in the epidermis
Sense pathogens via cell surface receptors and help mediate an immune response
Produce antimicrobial peptides that directly kill pathogens
Produce cytokines and chemokines
How can keratinocytes be activated?
UV light and sensitizers
Main skin resident immune cell
Langerhans cells
Birbeck granule
Tennis racket shaped characterisation of the antigen presenting cells Langerhans cells
Function of Langerhans cells
Process lipid antigen and microbial fragments and present them to effector T cells
Help activate T cells
What type of T cells are mainly found in the epidermis?
CD8+ T cells
What type of T cells are mainly found in the dermis?
CD4+ T cells and CD8+ T cells
CD4+ T cells associated with inflammation
TH1 (psoriasis), TH2 (atopic dermatitis) and TH17 (psoriasis and atopic dermatitis)
Where are T cells produced and sensitised?
Produced in bone marrow, sensitised in the thymus
What does antigen recognition and T cell activation involve interaction between?
T cell receptor and major histocompatibility complex, enhanced by co-receptors
2 co-receptors in interaction between T cell receptor and major histocompatibility complex
CD4+ helper T cells and CD8+ cytotoxic T cells
Function of TH1
Activate macrophages to destroy microorganisms
Function of TH2
Help B cells to make antibodies
Function of CD8+ cytotoxic T cells
Kill infected cells directly
Dendritic cells found in the dermis
Dermis dendritic cell and plasmacytoid dendritic cell
What is produced by plasmacytoid dendritic cell?
IFN-alpha
True or false: plasmacytoid dendritic cells are found in healthy skin
False - they are found in diseased skin
What transmits information from dendritic cells to T and B cells?
Antigen presenting cells
True or false: macrophages, neutrophils and mast cells are found in the dermis
True
Where is the major histocompatibility complex found?
Chromosome 6
Class I histocompatibility complex:
- Which cells is it present on?
- Which T cells does it present the antigen to?
- What type of antigen does it present?
- What can it detect?
Present on almost all cells
Presents antigen to cytotoxic T cells
Presents androgynous antigen
Can detect intracellular antigens
Class II histocompatibility complex:
- Which cells is it present on?
- Which T cells does it present the antigen to?
- What type of antigen does it present?
Present on antigen presenting cells
Presents antigen to helper T cells
Presents exogenous antigens
True or false: the major histocompatibility complex is involved in immunological recognition and transplant rejection
True
Examples of skin conditions associated with inappropriate immune responses/inflammation
Psoriasis Atopic dermatitis Bullous pemphigoid Contact dermatitis Morphea/systemic sclerosis Urticaria SLE Skin infections Skin tumours
Which CD4 cells make IL-17?
TH1 and TH17
What things can lead to autoimmunity?
Lymphocyte abnormalities Intercell communication Genetic predisposition Anatomic alterations Hormonal influence Infections
Examples of skin conditions that are autoimmune
Psoriasis, vitiligo and systemic lupus erythematosus
Primary immunodeficiency is __ and secondary immunodeficiency is __
(acquired and genetic)
Primary immunodeficiency is genetic
Secondary immunodeficiency is acquired
Causes of secondary immunodeficiency
AIDS Malignancy Ageing Diabetes Renal malfunction Burns Alcoholic cirrhosis Malnutrition
Type I hypersensitivity is __ mediated
Antibody - IgE
Describe type I hypersensitivity - early exposure and later exposure
Early exposure to antigen causes IgE production, which binds to FcεR1 receptor on mast cells.
Later exposure causes rapid cross-linking of the receptors, signal transduction and degranulation of the mast cell
Type II and type III hypersensitivity reactions are __ mediated
Antibody - IgG and IgM
When are type II hypersensitivity mechanisms important?
Autoimmunity and transplantation e.g. haemolytic disease of the newborn and blood transfusion recipients
Skin testing in type III hypersensitivity reaction leads to what?
An Arthus reaction
Type IV hypersensitivity is __ mediated
T cell
Describe type IV hypersensitivity reactions
Delayed type hypersensitivity is based on T-cell mediated response, which then recruits other cells to the site and peaks 24-48 hours after contact with antigen
Factors that can affect skin immune response
Organ transplant, UV, ageing
How does organ transplant affect the skin immune response?
Immunosuppression
How does UV affect the skin immune response?
Immunosuppression
Affects the structure of the skin
How does ageing affect the skin immune response?
Changes in skin structure
Decreased ability to detect malignant cells
Decreased ability to detect antigen infection risk
Decreased ability to distinguish self from non-self - autoimmunity
