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Clinical pathology 2 > Immune function > Flashcards

Immune function Flashcards

1
Q

Immune system

A

body’s defense system. Involves collection of barriers, cells and protein mediators that interact with one another to fight disease

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2
Q

Two forms of immunity

A

Innate: present before birth

Adaptive/ acquired: developed as a result of exposure to pathogens

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3
Q

Cells of the immune system

A

All arise in the bone arrow from hematopoietic stem cells which divide and replace the different blood cells through a persons life. These stem cells mature to become progenitor cells
phagocytic cells
lymphocytes ( B , T and natural killer cells)
granulocytes ( basophils, neutrophils, eosinophils)
erythrocytes (red blood cells)

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4
Q

Innate immunity

A

first defense
less specific than acquired immune system
consists of :
physical barriers ( prevent pathogens from entering body tissue)
cells: attack and eradicate pathogens from the body
humoral mediators: macromolecules that assist in the immune response

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5
Q

Cells associated with the innate immunity and their function

A 
phagocytes:
neutrophils:
eosinophils:
basophils:
natural killer cells:
mast cells:
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6
Q

Monocytes

A

precursor cells that differentiate into either dendritic or macrophages

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7
Q

Dendritic cells aka antigen presenting cells

A

sentinel cells
able to recognize the presence of pathogens
once they detect pathogens they become activated
once activated they are able to migrate to the lymphoid tissue where they are involve in the antigen presentation
they are found in many tissues in the body and are known by different names depending on which organ they are occupying

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8
Q

Dendritic cells other names

A

Kupffer cells- spleen and liver
Langerhans- skin
Mesangial cells-kidney
Microglial cells-brain

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9
Q

Dendritic cells become activated when antigens are detected by

A

toll-like receptors
heat shock protein receptors
cytokine receptors

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10
Q

Humoral mediators

A

macromolecules found in the extracellular fluids of the body

often interact with the cellular components of the immune system

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11
Q

Some humoral mediators of the innate system are

A

complement system: protein cascade that helps eliminate pathogenic organisms. Involved in both immunities. Activation leads to cytolysis chemotaxis, opsonization and inflammation in addition to marking pathogens for phagocytosis
arachidonic acid: polyunsaturated fatty acid involved in cellular signaling, inflammation and vasodilation
cytokines: allow cells to communicate with one another
are a group of small proteins involved in cell signaling. Regulate balance between humoral and cellular components of the immune system. Control maturation, growth and responsiveness of various cell populations

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12
Q

Examples of cytokines

A

IL-1
IL-2
TNF alpha

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13
Q

How innate immunity works

A

Innate response occurs immediately upon infection or injury and results in inflammation
Sentinel cells ( macrophages and dendritic cells) in the tissues detect the presence of pathogens through a number of receptors
This initiates the secretion of pro-inflammatory cytokines, the main ones being IL-1 and TNF alpha and several other mediators. The IL-1 TNF alpha and other mediators act on the capillary endothelial cells resulting in increased vasodilation and vascular permeability. They also stimulate the expression of adhesion molecules on the endothelial surfaces
The increased vascular permeability results in an exudate that contains the components of four proteolytic enzyme cascades including the complement system
By means of adhesion molecules the leukocytes roll on, adhere to and migrate through the vascular endothelium into the tissue and move towards the pathogen, attracted by chemokines IL-8 and C5a
Once they encounter a pathogen, they phagocyte and kill it

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14
Q

The complement system

A

consist of 9 major components C1-C9

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15
Q

Methods to activate complement system

A

classical: initiated when C1 interacts with antigen-antibody ( part of acquired immunity) complexes which activates the C3
lectin binding and alternative pathways directly activate C3 by the surfaces of many pathogens or by substances derived from microorganisms They form part of the innate system

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16
Q

Activation results in the splitting of C3 into

A

C3a : then stimulates mast cells to release additional chemical mediators ( e.g. histamine) and attracts phagocytes at the site of infection
C3b: are able to attach to the surface of microorganisms in a process called opsonization
Also acts on C5 producing C5a which stimulates release of further mediators from mast cells
It is a chemical attractant of leukocytes drawing them toward site of infection

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17
Q

Opsonization

A

facilitates phagocytosis and is important in antigen presentation to naïve B cells

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18
Q

Membrane attach complex

A

a number of complement components come together to form this membrane attack
it is able to attach to the membrane of some bacteria
This causes lysis and therefore the direct destruction of some bacteria

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19
Q

Functions of complement system

A

binds to pathogens labelling them for phagocytosis (opsonization)
acts as a chemotactic agent to attract phagocytic cells
creates pores in the membranes of the pathogens killing them

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20
Q

Acquired immune system

A

responds more slowly to infections
highly specific for different pathogens
after exposure to a pathogen, subsequent exposure to the same pathogen will be quicker and more powerful

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21
Q

Two types of cells in the acquired immune system

A

controlling cells- T cells / lymphocytes

antibody-producing cells - B cells

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22
Q

T lymphocytes

A

group of cells that mature in the thymus gland
central to the coordination of the immune response to invading pathogens
80% lymphocytes are T cells

23
Q

Various T cells have the ability to either

A

secrete macromolecules that enable communication between the various cells of the adaptive immune response
eliminate cells infected with intracellular pathogens

24
Q

3 main classes of T cells

A

T helper cells- bearing CD4 ( active B and other T cells)
T cytotoxic cells- bearing CD8 ( attach to and kill cells that have the antigen they are programmed to recognize)
natural killer cells ( release cytotoxic granules of cause apoptosis in target cell using Fas ligand) They are considered to be T cells though they lack T-cell receptors

25
Q

Two general phases to the acquired immune response

A

Induction phase:

Effector phase

26
Q

Induction phase

A

T cells with either CD8 or CD4 are presented with antigen by APCs. The APCs which have either ingested or are infected with pathogens process the antigens and present them on their surface in combination with MHC molecules The T cell receptor in conjunction with CD8 or CD4 recognizes antigen displayed by the MHC 1 and MHC 2 molecules. The interaction of CD8 and TCR with antigen presented by a MHC1 molecule causes the cells to become activated cytotoxic T cells that are able to recognize and kill virally infected cells . The T helper cells bearing CD4 are activated when their T cell receptors and the CD4 co-receptor bind MHC 2 and antigen. Once Th cells become activated they proliferate but they require a week to become effector TH cells. The effector Th cells either release cytokines that activate macrophages or other immune cells or stimulate B cells to proliferate. The effector Th cells differentiate into cells that releases different types of cytokines

27
Q

Role of Natural killer cells in Induction phase

A

NKC kill pathogens by releasing lysosome granules into the cell or by inducing apoptosis in the target cell. Natural killer cells do not require co-stimulation by other molecules or cells. Instead, they act alone. They can however become activated. This stimulates them to enlarge and increase their killing capacity

28
Q

Memory cells

A

Activated T and B cells can differentiate into memory cells or plasma cells. The memory T cells can reactivate if the antigen is encountered again. This explains the faster response of the immune system when an individual is infected with the same pathogen a second time. In some cases the response to subsequent infections is so efficient that the pathogen is killed before it can cause illness. Immunization makes use of this capability

29
Q

B lymphocytes

A

are involved in the immunoglobulin ( antibody) response to invading pathogens. When they are activated they produce antibodies that will bind and coat foreign particles of molecules. They are effective in the extracellular fluid but cannot bind pathogens within cells

30
Q

Five types of immunoglobulin or antibodies, which differ structurally are

A 
IgG ( most common)
IgM
IgA
IgE
IgD
31
Q

Antibodies increase the effectiveness and specificity of host defence by

A

activating the complement system when the antibody-antigen complexes are formed ( classical pathway of activation
binding to antigens on the surface of pathogens. This exposes the Fc domain of the antibody, which is recognized by phagocytic cells, facilitating
activating natural killer cells ( recognize antibodies bound to antigen and can become activated)
Binding to toxins preventing them from interacting with cells

32
Q

What happens during maturation of B cells

A

dendritic cells present antigen-antibody complexes to immature B cells. This process results in a mature B cell that manufactures a specific antibody which it displays on its surface. This antibody will recognize a particular antigen. If the B cell- then encounters the antigen ( binds to its antibody) it will divide and secrete a soluble form of the antibody. These activated B cells are known as plasms cells. All antibodies recognize and interact with a specific antigen and activate further components of the immune system

B cells can also present antigens to T cells
This stimulates the T cells to release cytokines which further act on B cells

33
Q

Major histocompatibility complex MHC

A

MHC molecules are important in the activation of T cells because they present processed antigens to them. The MHC molecules are encoded by the HLA genes found on chromosome 6.

34
Q

MHC molecules can be divided into two types

A

MHC class 1 : expressed on all nucleated cells and present endogenous antigen to Tc cells

MHC class 2: present exogenous antigen to Th cells and are generally only expresses on APCs

These cells have a system to ensure that all self-antigens are recognized and therefore not presented by the MHC molecules. This ensures that the immune system does not attack the organisms own cells

35
Q

Transplant rejection arises when

A

recipients immune system rejects the transplanted tissue. This results in the transplanted tissue being damaged. The chance of transplant rejection can be reduced by ensuring that the donor and recipient have similar MHC compositions. Immunosuppressant drugs can be administered after new tissue is transplanted to reduce the recipients immune response to the new organ

36
Q

Three different types of tissue rejection

A

Hyperacute- occurs within minutes, antibody-mediated reaction
Acute- develops within days; driven by both humoral and cell-mediated reactions
Chronic- evolves over months, cell mediated reaction

37
Q

Reticuloendothelial system

A

found throughout the body and includes:
bone marrow
lymphoid organs ( lymph nodes, spleen, thymus) mucosa
lymphatic vessels

38
Q

Bone marrow

A

Hematopoiesis occurs here ( adults)

immature lymphocytes then move to the lymphoid organs where they mature

39
Q

Lymph nodes

A

Lymph drains from around the body into the lymph nodes
function- to remove microbes and debris from the lymph
Any pathogens that enter the lymph node are phagocytized and killed by dendritic cells and macrophages
Also important in activation of B and T cells

40
Q

How

A

lymph

41
Q

Spleen

A

filters blood from the splenic artery.
macrophages and dendritic cells remove pathogens and other material from the blood
This process is vital in fight against blood-borne pathogens

42
Q

Mucosa-associated lymphoid tissue MALT

A

this tissue is associated with the mucous membrane epithelia of the GI tract

43
Q

Immune system disorders divided in 3 namely

A

Hypersensitivity reactions
autoimmune diseases
immunodeficiency syndrome

44
Q

Hypersensitivity reactions

A

due to excessive immune responses
4 types:
Type 1- allergic and anaphylactic responses
Type 2- fixed antigen or antibody mediated hypersensitivity
Type 3- immuno-complex mediated hypersensitivity
Type 4- delayed cell-mediated hypersensitivity

45
Q

Autoimmune diseases

A

occur when there is an abnormal immune response and body fails to discriminate self-antigens from non-self antigens

46
Q

Immune tolerance

A

ability of immune system not to react against itself

47
Q

Tolerance can be classified as either

A

Central or peripheral

48
Q

Central tolerance

A

primary mechanism the body uses to differentiate between self and non-self. Involves deletion of self-reactive lymphocyte clones (B and T cells) before the cell becomes fully immunocompetent

49
Q

Peripheral tolerance

A

when the B and T cells enter the lymph nodes and their reactivity to self antigens they have not previously been exposed to is tested. If they are self-reactive they are eliminated

50
Q

Immune deficiency syndrome may be

A

primary ( genetic) or secondary ( acquired)

51
Q

Primary immunodeficiencies

A 
arise because of malfunction in either the cellular or humoral aspects of the immune system as a result of genetic defects. They occur early in life and re detected primarily in children who have repeated severe infections
Examples:
SCID ( severe combined immunodeficiency)
IgA deficiency
DiGeorge syndrome
Wiskott-Aldrich sysndrome
52
Q

What cells co-ordinate the entire immune system?

A

T -cells. Defects in T cells result in susceptibility to all type of infection
Neutrophil, complement or B cell defects are more likely to result in repeated bacterial infections

53
Q

AIDS

A

caused by HIV and results in progressive T-cell loss. The clinical expression of the disease is due to secondary opportunistic infections because of an impaired immune system

Clinical pathology 2 (6 decks)

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