Innate to Adaptive Immunity Flashcards Preview

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Flashcards in Innate to Adaptive Immunity Deck (36)
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How much protective, anti-bacterial proteins does an average human produce each day?

5 grams. They are mostly members of the defensin and cathelicidin families. They are positively charged (CATionic HELICal) and attach themselves to the negatively charged pathogen membranes, opening lethal pores in the membranes.


What is the role of the immune system?

Its job is to detect intruders in the body and arrange for their inactivation, destruction, and removal. It makes a strong effort to distinguish innocent and evil invaders, but sometimes overreacts to harmless particles such are pollen or food.


What animals have innate immunity and how does it function?

Most animals, including invertebrates, have innate immunity. It recognizes molecular motifs found in pathogens but not in the host itself. These motifs include bacterial cell walls and odd microbial nucleic acid structures.


What three things does innate immunity recognize?

PAMPs - Pathogen Associated Molecular Patterns (Foreign molecular structures) DAMPs - Damage Associated Molecular Patterns (expressed by cells encountering stress or damage) and the ABSENCE of certain normal cell surface molecules (by NK cells)


How does the innate immune system recognize PAMPs and DAMPs?

By the presence of Patter Recognition Receptors (PRRs), including Toll Like Receptors (TLRs), located on the surface of nearly all cells. The Toll gene is what confers innate immunity to invertebrates, humans have 10 Toll-like genes.


What are three TLRs and what do they individually recognize?

TLR2 - recognizes peptidoglycan on Gram-positive bacterial walls, TLR3 - binds double stranded RNA, TLR4 - recognizes lipopolysaccharides on Gram-negative bacterial walls.


How do TLRs trigger an immune response?

When a TLR binds its target it triggers a signaling cascade that results in the activation of NF-kB, "the mother of all inflammatory transcription factors". NF-kB up regulates transcription of cytokines and chemokines.


What is the definition of inflammation?

Increased blood vessel diameter, stickiness, and leakiness, with an efflux of fluid and phagocytic white blood cells into the tissues. The intent is to quickly get defense and healing agents into the damaged or invaded areas.


How quick is the innate immune response, and what is a limitation of the system?

The innate immune response is fast acting. Many inflammatory mediators, especially the chemokines, are chemotactic for phagocytic while blood cells and attract them from distant areas. However, it cannot adapt to totally new challenges, it only knows its established patterns.


What is the connection between the innate and adaptive immune systems?

Dendritic cells are phagocytic cells that lie at the boundaries of the body and the outside world. They generally exist in an immature form, are activated by the cytokines and chemokines, rapidly mature and begin to ingest anything they can, including pathogens. They cannot be activated without an innate system response.


How do activated (mature) dendritic cells activate the adaptive immune system?

Activated DC leave the periphery and travel to the nearest lymph node, where they present (they are termed "antigen-presenting-cells") the antigens they have phagocytosed to the T and B cells present in the node. The adaptive response cannot develop in the periphery, the DCs must bring the antigens to the organized lymph nodes.


What are the cells of the adaptive immune system and what do they do?

There are lymphocytes and phagocytes. Lymphocytes are specialized for the recognition of foreignness, and phagocytes are specialized for eating and digestion.


How do lymphocytes do their job?

Lymphocytes have specialized receptors that bind to antigenic molecules (epitopes or "antigenic determinants") who fit the best. A LC may have 100,000 receptors, but all are identical, thus one cell can only recognize one epitome. There may be up to 10^14 possible arrangements of receptors.


What is an antigenic determinant?

An antigenic determinant (or epitope) is a small (10-20 AA) part of a larger antigenic molecule. This is the part that is recognized by the lymphocyte receptors. The lymphocytes exist BEFORE the antigen is present, and the antigen may encounter millions of other lymphocytes before it is recognized by one.


What happens after an antigen binds a lymphocyte?

The lymphocyte becomes activated and begins rapidly dividing (~6hr doubling time, called a "clone"). Some cells of the clone differentiate and begin to secrete proteins that activate the immune response. Once the clone is large enough, we can fight the infection and begin to recover. A subset of the clones are long lived, so the factory remains expanded, offering faster response times the next time the antigen is encountered. This is immunity or immunologic memory. These "memory cells" are also easier to activate, thus they are faster acting.


What are the two kinds of adaptive immunity and the two types of cells that specialize in it?

Two types of lymphocytes feature in adaptive immunity: T and B cells. They both recognize and remove foreign substances. B cells protect the extracellular spaces (fluids, blood, secretions). T cells survey the surfaces of the body's cells, looking for antigens or parasites, or dangerously changed or mutated cells.


How do T cells function?

They recognize antigens with receptors on their surface, which see antigens presented by DCs. Activated T cells then produce a clone, and some members of that clone secrete short range mediators called "lymphokines" (cytokines produced by lymphocytes). These trigger an inflammatory response and activate monocytes and macrophages. Another type of T cell is specialized for killing body cells that contain abnormal molecules.


How do B cells function?

B cells also recognize antigens through cell receptors on their surface. They then become activated and replicate, and then begin secreting soluble versions of their receptors, namely antibodies, which go out and do the work.


How do resting T cells look compared to B cells?

All resting lymphocytes look the same.


6 types of T cells

Type 1 Helper, Type 17 Helper, Type 2 Helper, Follicular Helper, Regulatory, Cytotoxic (Killer)


What do Type 1 Helper cells do?

Type 1 Helpers recognize antigen and secrete lymphokines that attract thousands of macrophages to the area of the antigen. This greatly increases inflammation and can repel an infection, or a transplanted organ.


What do Type 17 Helper cells do?

Type 17 Helpers are similar to Type 1 in that they cause inflammation, but they are more powerful than Type 1. They resist very tough infections, but also are implicated in serious autoimmune disorders.


What do Type 2 Helper cells do?

Type 2 Helpers stimulate macrophages to become "alternatively activated". They also function in walling off pathogens and promoting healing after the Type 1 response. Also active in parasite immunity.


What do Follicular Helper cells do?

After activation by antigen presenting cells, they migrate from the T cell areas of nodes to the B cell areas and help activate B cells to produce IgM, IgG, IgE, and IgA antibodies.


What do Regulatory T Cells do?

Regulatory T Cells make lymphokines that suppress the activation and function of other T helper cells, keeping the immune response in check.


What do Cytotoxic or Killer T Cells do?

Cytotoxic cells kill any body cell they identify as bearing a foreign or abnormal antigen on its surface.


What cell surface markers do the T Helper and T Killer cells have on their surfaces?

The T Helper cells display CD4 and the T Killer cells display CD 8. These markers increase their affinity for antigen, helps them get activated, and serves as a convenient ID tag.


How are Helper and Killer cells activated?

Helper cells are activated when antigens are presented on MHC Class II molecules. Killer cells are activated when antigens are presented on MHC Class I molecules. The activated killer cells may then replicate and seek out other body cells (all of which have MHC I) that are infected.


What are the five classes of antibodies?

IgM, G, D, A, & E


What does IgG do?

IgG is the most common antibody in the blood. Two adjacent IgG molecules, binding antigen, can activate the complement, as system of proteins that enhances inflammation and pathogen destruction. It is also the only antibody that can diffuse through the placenta and is critical in protecting a newborn until it can make its own IgG.