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*Immunology > Intro to Immunity > Flashcards

Intro to Immunity Flashcards

1
Q

Antigens

A

biochemical components (proteins, carbohydrates, lipids, and nucleic acids) that alert leukocytes to their presence within the body. Leukocytes recognize antigens via antigen receptors displayed on the leukocyte surface

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2
Q

When a leukocyte binds to an antigen via its antigen receptor, the interaction induces the leukocyte to eliminatevantigen by one or more mechanisms:

A

phagocytosis, cytotoxicity, synthesis of soluble factors

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3
Q

Phagocytosis

A

ingestion and enzymatic digestion of particulate antigens, e.g.,microbes, allergens, damaged host cells, etc.

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4
Q

Cytotoxicity

A

induction of lysis and/or apoptosis of microbe-infected host cells, tumor cells, or mismatched tissue grafts

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5
Q

Synthesis of soluble factors

A

production of antibodies, complement components, defensins, cytokines, and other substances that help eliminate the foreign antigen

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6
Q

How do immunologists separate the immune system?

A

Innate versus adaptive immunity

Humoral versus cell-mediated immunity

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7
Q

Innate immunity

A

includes all host defenses that are present and functional at birth, including natural barriers like skin, and leukocytes whose antigen receptors have broad specificity, e.g., phagocytes, granulocytes, NK cells. Complement/CRP/defensins/cytokines, pattern rec receptors, normal flora

broadly identifies groups of antigens, rapid response, no memory, unaffected by vaccination

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8
Q

Adaptive immunity

A

develops slowly in response to host contact with a specific antigen and includes just four major components: antibodies, B lymphocytes, plasma cells, and T lymphocytes.

very specific, slow response, memory, improved by vaccination

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9
Q

Immunological memory/Clonal Selection Theory

A

the increase in speed and strength with which B and T lymphocytes respond to an antigen upon re-exposure to that same antigen. Immunological memory can be explained by the Clonal Selection Theory, which states that a given antigen will induce proliferation and differentiation only of those B and T lymphocytes that have receptors specific for that antigen. Some of the responding B and T lymphocytes will develop into memory cellsthat can survive for years within the lymph nodes. Memory cells undergo rapid activation and expansion when they encounter the same antigen againat a later time, resulting in greater numbers of antigen-specific lymphocytes with higher affinity antigen receptors than in previous encounters.

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10
Q

Humoral immunity

A

mediated by soluble proteins and glycoproteins present in serum and the extracellular tissue fluids. It is most effective against extracellular pathogens rather than pathogens that live inside host cells

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11
Q

Cell-mediated immunity(CMI)

A

is mediated by “effector cells” that directly kill intracellular and extracellular pathogens, tumors, and damaged host cells by phagocytosis or cytotoxicity.

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12
Q

The most important humoral immune factors are:

A

Antibodies (immunoglobulins)***–highly antigen-specific glycoproteins produced by B cells and plasma cells

Complement –a series of serum proteins that work together to lyse bacteria and other pathogens

C-reactive protein (CRP) –a general marker for inflammation or infection

Cytokines –soluble proteins that are used for communication between leukocytes

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13
Q

The most important effector cells in CMI are:

A

Phagocytes that engulf and kill extracellular pathogens using enzymes and reactive oxygen species generated within the phagolysosome. The most efficient phagocytes are neutrophils and monocytes/macrophages.

Granulocytes that release enzymes and reactive oxygen species from granules to kill extracellular pathogens. The most efficient granulocytes are neutrophils, eosinophils, and basophils.

Cytotoxic cells that release enzymes and use receptors on their surfaces to induce apoptosis in infected host cells or tumors. The most important cytotoxic cells are natural killer cells (NK cells) and cytotoxic/cytolytic T cells (Tc cells).

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14
Q

Antibody, complement component C3b, and CRP are opsonins. Opsonins are….

A

substances that coat bacteria and other particulate antigens to aid their recognition and ingestion by phagocytes. Many bacteria have capsules that protect them from phagocytosis. However, when the capsules become coated by opsonins, the capsules no longer provide protection against phagocytosis.

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15
Q

Leukocytes

A

White blood cells that carry out the functions of the immune system. They develop by the process of hematopoiesis from self-renewing hematopoietic stem cells in the bone marrow.

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16
Q

CD34 and Stem cell antigen-1 (SCA-1)

A

these markers are used clinically to enrich stem cells for transplantation and immune reconstitution

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17
Q

The two major lineages of leukocytes arising from hematopoietic stem cells are

A

myeloid and lymphoid

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18
Q

Lymphoid Cells

A

B lymphocytes

T lymphocytes

Natural killer (NK) cells

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19
Q

Myeloid Cells

A

Erythrocytes –oxygen transport to tissues

Platelets (from megakaryocytes) –blood clotting and inflammation

Granulocytes (neutrophils, basophils, eosinophils)

Phagocytes (neutrophils, monocytes/macrophages)

Antigen-presenting cells (dendritic cells, monocyte lineage)

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20
Q

Erythropoietin (EPO)

A

Reverse anemia (especially in renal failure) by restoring erythrocytes/RBCs

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21
Q

Granulocyte colony-stimulating factor (G-CSF)

Filgrastim

A

Recovery of bone marrow (PMNs)

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22
Q

Granulocyte-monocyte colony-stimulating factor (GM-CSF)

Sargomastim

A

Recovery of bone marrow (PMNs, monocytes, macrophages)

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23
Q

IL-11

Oprelvekin

A

Reverse thrombocytopenia (platelets)

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24
Q

Thrombopoietin

TPO

A

Reverse thrombocytopenia (platelets)

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25
Q

Mucosa-associated lymphoid tissue (MALT; secondary lymphoid tissue)

A

The MALT responds primarily to antigens that enter the body through mucosal surfaces. B lymphocytes in the MALT produce mainly secretory IgA, an antibody class that resists digestive enzymes found in the gut and other mucosal tissues.

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26
Q

Examples of MALT

A
  • Gut-associated lymphoid tissues (GALT): lines intestinal tract
  • Bronchus-associated lymphoid tissue (BALT): lines respiratory tract
  • Genito-urinary tract-associated lymphoid tissue (GU-ALT)
  • Specific tissues include the lamina propria, tonsils, adenoids, appendix, and Peyer’s patches. Peyer’s patches are loose clusters of lymphoid tissue in the small intestine. M cellsare epithelial cells overlying Peyer’s patches specialized for transcytosis of antigens from the lumen to subepithelial T cells.
27
Q

White Pulp of spleen

A

comprises the lymphocyte-rich regions of the spleen. It contains:
T cells arranged in a periarteriolar lymphoid sheath (PALS)around a central arteriole
B cell-rich follicles(some containing germinal centers) occupying the space between the PALS and the marginal sinus
A marginal zone at the outer boundary of the white pulp. The marginal zone contains specialized macrophages and additional B cells

28
Q

Red Pulp of Spleen

A

contains plasma cells, resident macrophages, erythrocytes, platelets, granulocytes and lymphocytes. Its main function is hemocatheresis, the destruction of aged platelets and erythrocytes. Iron recycled from erythrocytes is stored here.

29
Q

Spleen

A

responds primarily to blood-borne antigens. It is the major organ where antibodies are synthesized and released into circulation. Asplenic persons are highly susceptible to infection by encapsulated bacteria, e.g. Streptococcus pneumoniae, Haemophilus influenzae, Neisseria and Salmonella spp. This is because antibodies are needed as opsonins to neutralize the anti-phagocytic property of bacterial capsules. The spleen is located in the upper left quadrant of the abdomen.

30
Q

Medulla (of the lymph node)

A

Medullary cords contain closely packed lymphocytes and plasma cells

Medullary sinuses contain macrophages

Medullary sinuses communicate with the efferent lymphatics

31
Q

Paracortex of Lymph node (T cell area)

A

Lymphocytes in the blood enter the paracortex region of the lymph node through specialized post-capillary venules called high endothelial venules (HEVs)

HEVs contain specialized cuboidal cells that express adhesion molecules in high density

These adhesion molecules allow lymphocytes to bind tightly to the venule wall, and then extravasate from the venule to enter the node

The paracortex becomes greatly enlarged during extreme cellular immune responses. The paracortex is poorly developed in DiGeorge syndrome because affected individuals produce no/few T cells

32
Q

Cortex of Lymph Node (B cell area)

A

Primary folliclesin the cortex contain naïve B cells that have never contacted antigen

Secondary folliclesin the cortex contain germinal centerscomposed of B cells undergoing mitosis in response to antigen stimulation

33
Q

Lymph nodes (secondary lymphoid organs)

A

respond primarily to antigens entering through the skin and subcutaneous tissues. The functions of lymph nodes and the lymphatic system include:

  • Isolation of infectious agents and cellular debris from the body
  • Surveillance and filtration of the lymph by macrophages
  • Storage and activation of B and T cells
  • Antibody production by B cells
  • Maintenance of interstitial fluid pressure and volume by returning excess water and dissolved substances from the interstitial fluid to the circulation
  • many afferent vessels but only 1 efferent
34
Q

T cell education is the process by which

A

self-reactive T cells are eliminated and is essential for avoiding autoimmune diseases. T cell education takes place in the cortex and medulla of the thymus.

35
Q

Thymus (a primary lymphoid organ)

A

encapsulated organ that develops from the epithelium of the third and fourth pharyngeal (branchial) pouches. It is a bilobed structure that reaches its maximum size at puberty and then atrophies with age. THIS IS WHERE T CELL EDUCATION AKA REGULATION OCCURS

36
Q

DiGeorge Syndrome

A

Persons with a chromosome 22 deletion(22q11.2) are born with little or no thymus. These patients are highly susceptible to viral infections and cancer because they have few or no functional T cells.

37
Q

Process of T cell development

A
  • cell produced in bone marrow
  • cell travels to thymus: called double-negative thymocytes (have no CD molecules)
  • cell in cortex develops both CD4 and CD8 becoming a double-positive thymocyte
  • cell in medulla loses expression of one CD and becomes single positive cell
38
Q

Primary Lymphoid Organs

A

bone marrow

thymus

39
Q

Secondary Lymphoid Organs

A

spleen, lymph nodes, MALT

40
Q

Bone Marrow

A

where B cells begin expression of surface immunoglobulin molecules

41
Q

Megakaryocyte

A

large cell with a lobulated nucleus found in the bone marrow that gives rise to platelets (thrombocytes)

42
Q

Platelets/thrombocytes

A

are anucleate cells that promote blood clotting and inflammation. They bind to collagen exposed on damaged endothelial cells, forming microthrombi.

43
Q

complete blood count (CBC)

A

reveal whether a patient has a normal absolute number of circulating white blood cells (WBC). The typical range in adults is 4500-10,800 WBCs/mcL

44
Q

Leukocytosis

A

higher than normal WBC count

indicates infection, inflammation, leukemia, or trauma

45
Q

Neutrophil

A

purple

EC bacteria

live 2-3 days in circulation die in tissues

IgG receptors

46
Q

Eosinophil

A

red

worms

hypersensitivity, IgE

47
Q

Basophil

A

purple-black

worms

hypersensitivity, histamine, IgE

48
Q

Mast Cell

A

purple

worms

hypersensitivity, histamine, IgE

49
Q

List the polymorphonuclear Granulocytes

A

Neutrophil, Eosinophil, Basophil, Mast Cell

50
Q

Polymorphonuclear (PMN) granulocytes

A

short-lived cells that contain a multi-lobed nucleus and granules rich in enzymes (e.g.,lysozyme) and other substances (e.g.,lactoferrin) that are harmful to microorganisms. Granulocytes also produce reactive oxygen species.

51
Q

Dendritic cells

A

related to macrophages and are found under the epithelia and in most organs. In the skin, they are called Langerhans cells. Dendritic cells are the most efficient antigen-presenting cells (APCs). They are necessary for activating naïve T cells (T cells that have never before encountered antigen).

52
Q

Monocytes and macrophages (mononuclear phagocytes)

A
  • Circulating monocytes develop into tissue-fixed macrophages
  • The reticuloendothelial system (RES) is a network of tissue-fixed macrophages that remove foreign substances from the bloodstream and lymph
  • 10-18 μm diameter, horseshoe-shaped nucleus, long-lived
  • Functions are phagocytosis, antigen processing, andantigen presentation
53
Q 
Example of Monocytes/macrophages of the mononuclear lineage:
Kuppfer
Alveolar macros/dust cells
Splenic macros
Peritoneal Macros
Microglial cells
Osteoclasts
Mesangial cells
Synovial A cells
A 
liver
lung
spleen
peritoneal
brain
bones
kidneys
joints
54
Q

Phagocytosis

A

recptor ligand interaction initiated

macro pseudopods engulf bacterium/form phagosome

phagosome fuses with lysosome=phagolysosome

lysozymes destroy PDG of bacterial cell wall and ROS damage pt and DNA

end of bacteria

55
Q

Antigen processing

A

destruction of bacteria within a phagolysosome

Peptides specific to the destroyed bacteria are paired up with MHC, transported to cell surface, and used for T cell (antigen) presentation. Now cell is called APC

56
Q

Natural killer (NK) cells

A

part of the innate immune system.

eliminate infected host cells (especially virus-infected cells) and tumor cells, so they are very similar to Tc cells in this regard.

NK cells work most efficiently when the CD16 molecules on the NK cell surface bind to IgG-coated target cells. This collaboration between NK cells and IgG is called antibody-dependent cell-mediated cytotoxicity (ADCC). (Also CD56)

57
Q

B lymphocytes

A

develop in the bone marrow of humans and the Bursa of Fabricius of birds. They can differentiate into short-lived plasma cells that secrete high quantities of antibodies (immunoglobulins) or into long-lived memory cells that express surface immunoglobulin (sIg). The main function of B cells is to mediate humoral immunity.

The antibodies they produce can:

Neutralize toxins and microorganisms

Opsonize microbes for phagocytosis

Activate complement, leading to microbe lysis

58
Q

T lymphocytes

A

mature in the thymus. The T cell receptor (TCR) for antigen binds mainly to protein antigens. A TCR-associated accessory molecule, CD3, mediates signal tranduction to the T cell nucleus, thus activating the cell after antigen engagement. Activated T cells secrete cytokines or become highly cytotoxic toward infected host cells or cancer cells.

Helper T, Regulatory T, Cytotoxic T

59
Q

Helper T cell (TH)

A

all are CD4+ (also CD3)

immunity by cytokine secretion

TH1:works with macrophages, NK cells and Tc cells to promote cell-mediated immunity

TH2:stimulates antibody production by B cells to promote immunity against worms and allergens

TH17:aidsclearance of extracellular bacteria and fungi

60
Q

Regulatory T Cells (Treg)

A

all are CD4+, CD25+ (CD3)

Regulates the functions of macrophages, NK cells, and other T cell subsets

Helps prevent autoimmunity via cytokine secretion

61
Q

Cytotoxic T (Tc) cell

A

all are CD8+ (CD3)

Kills infected (especially virus-infected) and neoplastic host cells (tumors)

Involved in rejection of mis-matched tissue grafts

62
Q

B Lymphocyte (markers and function)

A

CD19, CD20, CD21(and surface immunoglobulin, sIg)

antibody secretion - humoral immunity

63
Q

All T lymphocytes have what markers

A

CD3 and TCR

*Immunology (6 decks)

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