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Flashcards in Immunology Deck (27):
1

Organs of the Immune System

Primary Organs
-Stem cells from the yolk sac and Fetal Liver
-Bone Marrow
-thymus gland

Secondary Organ
-lymph nodes
-spleen
-mucosa-Associated Lymphoid Tissue (MALT)

2

Types of Antigens

1. Immunogen
2. Hapten (+carrier = immunogen)
3. Allergen
4. Tolerogen
5. Ligand

3

The three lines of Host Defenses

1. The covering of the body (skin and mucous membranes)
2. The innate immune response
3. The adaptive (aquired) immune response

4

What the skin and Mucous membranes provide the body

-unpleasant living conditions for microorganisms
via epidermis, Mucus, pH, enzymes

5

Mode of transmission for airway

-inhaled droplet
-spores

6

Mode of transmission for GIT

Contaminated water or food.

7

Microbial Recognition strategies

Recognition of microbial non-self
-detection of unique, conserved structures that are essential to microbial physiology (Molecular signatures of infection)

Pathogen-associated molecular patterns (PAMPs)
-lipopolysaccharide (LPS) of gram negative bacteria
-Peptidoglycan (PGN) of gram-positive bacteria

PAMPs are recognized by immune system receptors called Pattern Recognition Receptors (RRR) including toll-like receptors.

8

Toll-like Receptors (TLRs)

-a family of highly conserved type 1 transmembrane receptors
-essential for microbial recognition via PAMPs

N-terminal extracellular leucine-rich repect (LRR)
-This domain consists of 19-25 tandem LRR
-Each LRR is 24-29 amino acids in length
-LRRs form a horseshoe shape for ligand recognition

C-terminal intracellular signaling domain with homology to the interleukin-1 receptor (Toll/IL-1R= TIR domain)
-Protein-protein interaction module

9

Innate(natural, "Nonspecific") Immunity

-cellular and humoral factors
-no memory
-early in evolution, danger signals

Cellular Factors
-Phagocytic cells (neutrophils, macrophages, interdigitating dendritic cells)
-Cells with inflammatory mediators (basophils, mast cells, eosinophils)

Humoral Factors
-acute phase reactants (e.g. C-reactive Protein, Complement, Interleukin)
-Cytokinins (interferon-alpha)

10

Normal Blood Cell Types

Erythrocytes

Leukocytes
-Neutrophils
-Eosinphils
-Basophils
-Monocytes
-Lymphocytes

Platelets

11

Innate Immune Response

Results in inflammation

Cellular Sequence:
1. The tissue macrophage
2. The neutrophil

12

Adaptive(acquired, specific)

-humoral (immunoglobulin/antibody mediated)
-cell-mediated (T cell/lymphocyte effector)

13

Limb's of the Immune Response

-Afferent Limb
-Efferent Limb

14

Efferent 'Limb'

-the effector or 'killing' aspect
-in the humoral immune response, this is antibody molecules (that will engage the complement)

- in the cellular immune response this will be T-cytotoxic (Tc) CD8+ lymphocytes

15

Afferent 'limb'

-made up of the events that initiate the immune response. (Innate immunity to the interaction with T-helper (Th) CD4+ lymphocyte. This limb will have both humoral and cellular components in both the humoral and cellular immune response mechanisms.

16

Adaptive Immune Response 1

Antigen (and epitope) specific
Antigen presenting cells (APC) -(MHC +peptide)
-interdigitating dendritic cell
-macrophage
-B lymphocyte (B cell)

17

Major Histocompatibility Complex (MHC)

Makes two kinds of molecules in cells:
-class I (HLA-A, HLA-B, HLA-C)
-class II(HLA-DP, HLA-DQ, HLA-DR)

18

Class I MHC molecules

- the chains are of markedly different masses: a large alpha chain and a small beta-2 and microglobulin chain
-can hold only short peptides because the binding site is closed off

19

Class II MHC molecules

- the alpha and beta chains are almost of the same size
-can bind to peptides of different lengths, because the binding site is open at both ends.

20

Antibodies

-humoral immunity
-immunoglobin
-basic structure of monomeric antibody molecule:
-Four chains: two identical light chains (Kappa or Lambda) determine immunoglobulin TYPE

21

Immunoglobulin (Ig) molecules

-five classes: determined by the Heavy (H) chain ( delta, mu, gamma, alpha, epsilon)
-two types: determined by the light chain kappa, lambda
-Interchain and intrachain disulfide bonds are present between and within all chain.

Classes:
IgM - complement binding
IgG - placental transer, complement binding
IgA - secretory properties (MALT)
IgE - Mastocytophilic properties

22

The complement Cascade (Classic)

-Constant regions of 2 antibody molecules in the Antigen-antibody complex bind C1 - C4-C2-C3 (breaks down to C3a +C3b)
-products of C3 and C5 enhance neutrophil phagocytosis
-later molecules in the sequence, particulary C9 punch a hole in the bacterial membrane.

23

Alternative Pathway (more primitive)

-can be activated by other factors such as LPS (a PAMP)
-turns on the innate Immune response; and Complement plays a role here e.g. enhances phagocytosis (C3 and C5)

24

Other types of T-cells

1. Regulatory T cells
2. T helper 17 cells
3. TH3 cells
4. Natural Killer T cells
5. Follicular B Helper T cells

25

Regulatory T cells (Treg)

-formerly know as suppressor T cells, are subpopulation of T cells which down regulated the immune system, maintains tolerance to self-antigens, and down regulates autoimmune disease.

26

T Helper 17 cells (Th17)

- subset of T helper cells producing interleukin 17 (IL-17). They are considered developmentally distinct from Th1 and Th2 cells and excessive amount of the cell are thought to play a key role in autoimmune disease such as Mulitple sclerosis.

27

TH3 cells

- involved in mucosal immunity and protecting mucosal surfaces in the gut from nonpathogenic non-self antigens. They mediate this non-infammatory environment by secreting TGF-beta and IL-10.