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Introduction to Medical Sciences > Immunology 1 > Flashcards

Immunology 1 Flashcards

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USMLE® Step 1 flashcards
1
Q

What is the main difference between the Innate immune system and the adaptive immune system?

A

The Innate immune system is the first line of defence, it is non-specific. The adaptive immune system however is the second line of defence and is highly specific.

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2
Q

What are the two types of immunity?

A

Active immunity:
Antigens enter the body stimulating the innate and adaptive immune system to produce memory cells and antibodies. This provides long term protection.
Passive immunity:
Antibodies are transferred directly from mother to baby. This can be through the placenta or through breast milk.

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3
Q

Which immune cells are made through the myeloid lineage? Which immune cells are produced through the lymphoid lineage?

A

Myeloid lineage:
Polymorphonuclear leukocytes:
Neutrophils, Eosinophils, Basophils
Also, Monocytes and so Macrophages and Dendritic cells.

Lymphoid lineage: B lymphocytes, T lymphocytes and Natural Killer cells.

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4
Q

What is the role of neutrophils?

A

Principle phagocytic cell of innate immunity. They rapidly migrate to the site of infection and here they ingest microbes by phagocytosis, release oxygen free radicals. They degranulate releasing proteins with microbial properties e.g. lysozyme.

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5
Q

What is the role of eosinophils?

A

Defend against multicellular parasites and have a role in allergy and asthma.

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6
Q

What is the role of Basophils?

A

Involved in inflammatory allergic reactions. Release histamine.

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7
Q

What is the role of monocytes? What is there shape?

A

Circulate in the blood and act as phagocytes; kill pathogens also through free radial production, myeloperoxidase and inflammatory cytokines. They are effectors of the inflammatory response. They are precursors of macrophages. They have a been shaped nuclei.

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8
Q

What is of macrophages?

A

Phagocytosis, microbial mechanisms and antigen presentation to their cells.

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9
Q

What is the role of Dendritic cells?

A

Antigen present to naïve T cells to initiate the specific immune response.

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10
Q

What is the role of Mast cells?

A

Release histamine. Close association with allergy and inflammation.

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11
Q

How do Natural Killer cells kill pathogens? What substances do they release?

A

They induce apoptosis by binding to infected cells and tumour cells and release perforin and granzyme B to trigger apoptosis in the target cell.

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12
Q

What is the role of B cells?

A

Produce antibodies, antigen present and produce immunological memory.

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13
Q

What is the role of T cells?

A

Kill infected and tumour cells; generate immunological memory; initiate the cell-mediated adaptive immune response; play a role in development and regulation of cell-mediated immunity.

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14
Q

Where to T cells develop and mature?

A

Thymus

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15
Q

Where do B cells develop and mature?

A

Bone marrow

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16
Q

Where do mature lymphocytes encounter antigens/pathogens?

A

In secondary lymphoid tissue. This includes lymph nodes, spleen and lymphoid tissue in other sites (tonsils, appendix, adenoids, Peyer’s patches (in ileum), bronchial associated lymphoid tissue (BALT).

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17
Q

What is removed in the red pulp of the spleen?

A

Erythrocytes

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18
Q

What occurs in the white pulp of the spleen?

A

Lymphocytes are stimulated

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19
Q

Give examples of mechanical barriers to pathogens?

A

The skin and mucous membranes. There is competition from normal flora. Mucous traps pathogens and this is swept out of by cilia.

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20
Q

What are physiological barriers to pathogens in the body?

A

Acid in the stomach

Fever response inhibits pathogen growth

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21
Q

What is the role of lysozyme the innate immune system?

A

Lysozyme cleaves the bacterial cell wall.

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22
Q

What is humoral immunity?

A

Antibodies are produced by plasma cells.

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23
Q

What is cell-mediated immunity?

A

Immunity effected by T lymphocytes.

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24
Q

What is the role of macrophages in non-infected tissue?

A

Phagocytose dead and dying cells.

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25
Q

What is pus?

A

Accumulation of dead neutrophils

26
Q

What is opsonisation?

A

The pathogen is covered in opsins – can be antibodies to complement proteins. This makes the pathogen a bigger target for phagocytosis.

27
Q

Which complement protein can serve as an opsin?

A

C3b

MBL

28
Q

What receptor is used on macrophages to take up pathogens or cells coated in antibodies?

A

Fc receptor

29
Q

How are dendritic cells specialised?

A

They have receptors that can recognise patterns of foreign molecules e.g. clusters of sugars present on the surface of many pathogens.

30
Q

Which cell do Dendritic cells antigen-resent to?

A

Naïve T cells

31
Q

What does activation of Naïve T cells lead to?

A

Proliferation of T cells. It also causes B cells to proliferate and produce antibodies.

32
Q

Which cell do Macrophages antigen present to?

A

Primed daughter T cells of a T cell activated by a dendritic cell.

33
Q

What is the role of Fab?

A

Antigen binding region
The specificity of the antibody binding to its antigen is due to the folding of the Fab region, which matches the shape of the antigen molecule very precisely.

34
Q

What is the role of Fc?

A

This can bind to the Fc receptors on the surface of immune cells such as macrophages.

35
Q

What is the role of IgM?

A

Main antibody of primary responses. Best at fixing complement. Monomers of IgM serve as B cell receptors.

36
Q

What is the role of IgD?

A

Main receptor on Plasma Cells

37
Q

What is the role of IgE?

A

Antibody of allergy and antiparasitic cells

38
Q

What is the role of IgA?

A

Secreted into mucous, saliva and tears.

39
Q

What is the role of IgG?

A

The most abundant antibody in the blood. It is the main antibody used in secondary responses, neutralised toxins and opsonisation.

40
Q

How does the variable region create diversity?

A

The variable region is coded for by a variable gene, diversity gene and the joining gene. There is also a constant gene coding for the constant region. Diversity is created due to recombination of alleles for these genes.

41
Q

How many variable gene alleles are there?

A

43

42
Q

How many diversity gene alleles are there?

A

23

43
Q

How many joining gene alleles are there?

A

6

44
Q

How many constant gene alleles are there?

A

5: Alpha (A), Dela (D), Epsilon (E), Gamma (G) and Mu (M). These letters are used to group immunoglobulins: there is IgA, IgD, IgE, IgG, IgM

45
Q

What is somatic hypermutation?

A 
Somatic hypermutation is a cellular mechanism by which the immune system adapts to new foreign elements that confront it, as seen during class switching.
B lymphocytes have a high mutation rate. As a result, mutations can arise that mean plasma cells can produce antibodies that bind better to the pathogen and stimulate other cells better.
46
Q

What is class switching of antibodies?

A

A biological mechanism that changes a plasma cells production of antibodies from one class to another e.g. IgG to IgM

47
Q

Which immunoglobulin has no transmembrane domain and so is secreted so that it can encounter pathogens in the blood?

A

IgG

48
Q

What is the effect of opsonisation?

A

The Fab region of the antibody binds to the antigen. As a result, the Fc region of the antibody binds to the Fc receptor on a macrophage. As a result, opsonisation increases the chance of phagocytosis. Opsonisation also stimulates the complement pathway through activation by the classical pathway. This leads to lysis of the bacteria.

49
Q

What is the difference between the primary and secondary response?

A

Primary response – slower and also produces fewer antibodies. The main antibody produced is the IgM antibody. The slow rise of IgM is followed by a slow rise in IgG.
Secondary response – faster to occur. Produces a larger volume of antibodies. The main antibody produced is the IgG antibody (there is also a limited rise in IgM). This is due to an immunological memory.

50
Q

In what form does a T cell recognise an antigen?

A

When it is properly expressed on an MHC Class II receptor of an antigen presenting cell such as a dendritic cell.

51
Q

How do TCRs arise?

A

TCR – T-cell receptor. They arise from a recombination of genes, like antibodies, and so are very diverse. TCRs are not released on the cell but remain on the surface and exhibit proliferation in response to antigens they recognise.

52
Q

What is MHC?

A

Major Histocompatibility Complex. These are a antigen that help the body to recognise whether a cell is self or if it is foreign.

53
Q

What is VDJ recombination?

A

VDJ recombination is the process by which T cells and B cells randomly assemble different gene segments – known as variable (V), diversity (D) and joining (J) genes – in order to generate unique receptors (known as antigen receptors) that can collectively recognize many different types of molecule.

54
Q

What is MHC Class I?

A

Proteins present on nearly all cell that express endogenous antigens that are synthesised in the cytoplasm.

55
Q

What cells do not present MHC Class I?

A

Cells that are anucleate – erythrocytes for example do not express MHC Class I.

56
Q

What cell recognises MHC Class I?

A

CD8+ (cytotoxic T cell)

57
Q

What is MHC Class II?

A

Proteins found only on specific immune cells that are antigen-presenting such as natural killer cells, dendritic cells, macrophages and B cells. MHC Class II present exogenous antigens on these proteins following phagocytosis.

58
Q

What cell recognises MHC Class II?

A

CD4 (Helper T Cells)

59
Q

What does the binding to Helper T cells to B cell MHC Class II-antigen stimulate?

A

The development of plasma cells against that antigen.

60
Q

What is the best way to eliminate a viral infection?

A

Destroy the infected cell so that no more viruses are produced. This is done by killing cells that do not express MHC Class I by cytotoxic T cells.

61
Q

What is the best way to treat a bacterial infection?

A

Generate antibodies that will agglutinate bacteria and so increase the chance of phagocytosis. Helper T cells recognise MHC Class II cells leading to clonal expansion of B cells so that antibodies can be produced.

62
Q

What is a hypersensitive reaction?

A

Over-reaction of the adaptive immune response. An example includes that in a peanut allergy and asthma.

Introduction to Medical Sciences (43 decks)

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