Immunology Flashcards Preview

Physiology 209 > Immunology > Flashcards

Flashcards in Immunology Deck (27):

Organs of the Immune System

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

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


Types of Antigens

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


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


What the skin and Mucous membranes provide the body

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


Mode of transmission for airway

-inhaled droplet


Mode of transmission for GIT

Contaminated water or food.


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.


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


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)


Normal Blood Cell Types





Innate Immune Response

Results in inflammation

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


Adaptive(acquired, specific)

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


Limb's of the Immune Response

-Afferent Limb
-Efferent Limb


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


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.


Adaptive Immune Response 1

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


Major Histocompatibility Complex (MHC)

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


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


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.



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


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.

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


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.


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)


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


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.


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.


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.