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Foundations of health and disease > t cells and acquired immunity > Flashcards

t cells and acquired immunity Flashcards

1
Q

What is the function of cytotoxic (killer) T cells?

A

They search for and destroy target cells that bear non-self antigens presented in MHC class I context.

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2
Q

What is the function of helper T cells?

A

They secrete cytokines that bind to receptors on B cells and T cells to stimulate their activity.

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3
Q

What is the function of suppressor T cells?

A

They secrete signaling molecules that bind to receptors on other immune cells to terminate their activity, thus suppressing immune responses that are no longer needed.

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4
Q

What is the characteristic of memory T cells?

A

They persist for life in a semi-dormant state but rapidly re-activated on a second exposure to the antigen (pathogen) they are specific for. They bypass the need for the primary immune response on the second infection.

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5
Q

Where do T cells emerge as progenitor cells and where do they differentiate and mature?

A

T cells emerge in the bone marrow as progenitor cells but migrate to the thymus where they differentiate and mature.

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6
Q

What does CD stand for in the context of lymphocyte populations?

A

CD stands for cluster of differentiation.

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7
Q

What is the significance of CD markers in distinguishing lymphocyte populations?

A

CD markers are specific cell surface molecules used to distinguish between different leukocyte subtypes. They help identify the functional characteristics of lymphocyte populations.

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8
Q

What does a CD4+ cell express, and what type of T cell is it likely to be?

A

A CD4+ cell expresses CD4 and is therefore likely to be a T helper cell.

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9
Q

What does a CD8+ cell express, and what type of T cell is it likely to be?

A

A CD8+ cell expresses CD8 and is therefore likely to be a cytotoxic T cell.

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10
Q

What is observed in the antigen binding site of MHC class I and MHC class II complexes?

A

Diversity and a degree of polymorphism are observed in the antigen binding site of MHC class I and MHC class II complexes.

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11
Q

: What does the HLA gene complex encode for in humans?

A

The HLA gene complex in humans encodes for the major histocompatibility complex molecules found in somatic or antigen presenting cells.

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12
Q

What type of antigens do cytotoxic T cells respond to?

A

Cytotoxic T cells respond to antigens presented in MHC class I context.

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13
Q

How does a cytotoxic T cell recognize the antigen on an infected cell?

A

The T cell receptor on a passing cytotoxic CD8+ T cell engages with the peptide presented on the surface of an infected cell.

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14
Q

What is the role of the CD8 molecule on the cytotoxic T cell?

A

The CD8 molecule on the surface of the cytotoxic T cell “double checks” that the peptide is presented correctly by recognizing that the MHC class I molecule is from a matched allele.

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15
Q

Under what conditions will a cytotoxic T cell kill the target cell?

A

The cytotoxic T cell will only kill the target cell once these engagements (T cell receptor-peptide interaction and CD8-MHC class I recognition) are complete.

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16
Q

What type of antigens do helper T cells respond to?

A

Helper T cells respond to antigens presented in MHC class II context.

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17
Q

How does a helper T cell recognize the antigen on a professional antigen presenting cell (APC)?

A

The T cell receptor on a passing CD4+ helper T cell engages with the peptide presented on the surface of a professional antigen presenting cell.

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18
Q

What does the helper T cell do upon recognizing the antigen?

A

The helper T cell “double checks” the identity of the presenting cell before becoming activated to secrete molecular messengers (cytokines) that further promote immune responses.

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19
Q

Where are MHC class I molecules found?

A

MHC class I molecules are found on all nucleated cells.

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20
Q

Where are MHC class II molecules found?

A

MHC class II molecules are found only on antigen-presenting cells (e.g., macrophage, dendritic cell, B cell).

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21
Q

What type of T cells do MHC class I molecules present antigens to?

A

MHC class I molecules present antigens directly to CD8+ cytotoxic T cells.

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22
Q

What type of T cells do MHC class II molecules present antigens to?

A

MHC class II molecules present antigens to CD4+ helper T cells.

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23
Q

From where are the peptide fragments derived that are presented by MHC class I?

A

Peptide fragments presented by MHC class I are derived from intracellular antigens.

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24
Q

From where are the peptide fragments derived that are presented by MHC class II?

A

Peptide fragments presented by MHC class II are derived from extracellular antigens.

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25
Q

Where is the peptide fragment loaded onto MHC class I?

A

The peptide fragment is loaded onto MHC class I in the rough endoplasmic reticulum (ER).

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26
Q

Where is the peptide fragment loaded onto MHC class II?

A

The peptide fragment is loaded onto MHC class II in endosomal vesicles.

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27
Q

What is the purpose of the endogenous pathway of antigen presentation?

A

The endogenous pathway evolved to deal with intracellular infections, primarily caused by viruses.

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28
Q

Which type of MHC molecules are involved in the endogenous pathway?

A

The endogenous pathway involves the expression of class I MHC molecules.

29
Q

When are cytosolic peptides presented in the endogenous pathway?

A

Cytosolic peptides are presented constitutively, meaning they are presented all the time and not just during infection.

30
Q

What is the significance of most peptides presented in class I context being self-derived?

A

Most peptides presented in class I context are self-derived, meaning they come from the body’s own proteins. Therefore, they do not typically trigger an immune response.

31
Q

What is the purpose of the exogenous pathway of antigen presentation?

A

The exogenous pathway evolved to deal with extracellular infections, particularly those caused by pathogens outside the cell.

32
Q

Which type of MHC molecules are involved in the exogenous pathway?

A

The exogenous pathway involves the presentation of antigens by class II MHC molecules.

33
Q

Which immune cells are capable of class II MHC presentation in the exogenous pathway?

A

Dendritic cells, macrophages, and B cells are among the select group of immune cells capable of class II MHC presentation.

34
Q

How does the endogenous pathway of antigen presentation work?

A

The endogenous pathway involves intracellular protein degradation to peptides. The peptide antigen is then loaded onto the MHC Class I complex with the help of chaperone molecules in the endoplasmic reticulum. It is transported through the Golgi before being presented on the cell membrane.

35
Q

How does the exogenous pathway of antigen presentation work?

A

The exogenous pathway involves the degradation of pathogens in endosomes. The stabilizing molecule at the MHC Class II complex antigen binding site is replaced with a peptide antigen. The complex is then transported to the cell membrane for presentation.

36
Q

Why is it not possible for all potential antigen shapes to be encoded in the germline?

A

The number of potential antigen shapes that need to be recognized by T cell receptors is huge, making it impractical to encode all of them in the germline (genome).

37
Q

What is the structure of T cell receptors (TCRs)?

A

T cell receptors consist of an alpha and a beta subunit, forming a heterodimer known as αβTCR. The subunits are generated by randomly combining V/J/C (alpha) or V/D/J/C (beta) genomic regions. The V regions exhibit the greatest diversity, and all three mRNA “frames” can be used during translation.

38
Q

What are the components of T cell receptors?

A

T cell receptors consist of a variable antigen binding domain and a constant domain associated with the cell membrane.

39
Q

Are T cell receptors glycosylated?

A

Yes, similar to the B cell receptor, T cell receptors are glycosylated.

40
Q

How do T cell receptors differ from B cell receptors in terms of affinity maturation and C domain substitution?

A

Unlike B cells, T cells do not undergo affinity maturation, nor do they undergo substitution of C domains during the immune response.

41
Q

How does T cell receptor (TCR) rearrangement contribute to increased antigen binding diversity?

A

TCRs undergo rearrangement similar to the BCR, which results in increased antigen binding diversity.

42
Q

What is the role of CD4 and CD8 in TCR interactions with MHC?

A

CD4 and CD8 act as TCR co-receptors in MHC interactions. They help stabilize the interaction between the TCR and MHC molecules.

43
Q

Is CD4 or CD8 involved in signal transduction inside a T cell?

A

CD4 and CD8 primarily function as co-receptors in MHC interactions, but additional co-receptor molecules are involved in full signal transduction inside a T cell.

44
Q

What type of antigen do CD4+ T cells recognize?

A

CD4+ T cells recognize antigens presented in MHC class II context by professional antigen-presenting cells (APCs).

45
Q

What type of antigen do CD8+ T cells recognize?

A

CD8+ T cells recognize antigens presented in MHC class I context on infected body cells.

46
Q

What is the role of CD4+ T cells upon activation?

A

Upon activation, CD4+ T cells secrete a variety of chemical messengers that stimulate immune responses.

47
Q

What is the role of CD8+ T cells upon activation?

A

Upon activation, CD8+ T cells engage with and attack target cells by triggering apoptosis (cell death) and damaging the cell membrane.

48
Q

Which pathway do T cell receptors on CD4+ T cells typically respond to?

A

T cell receptors on CD4+ T cells typically respond to antigens derived from the exogenous pathway.

49
Q

Which pathway do T cell receptors on CD8+ T cells respond to?

A

T cell receptors on CD8+ T cells respond to antigens derived from the endogenous pathway.

50
Q

What is required for full activation of CD4+ T cells?

A

CD4+ T cells require stimulation by an APC before full activation occurs.

51
Q

What is required for full activation of CD8+ T cells?

A

CD8+ T cells require stimulation by an infected target cell AND a CD4+ helper T cell before full activation occurs.

52
Q

Where do B cells develop and partially mature?

A

B cells develop and partially mature in the bone marrow.

53
Q

Where do T cells originate and further develop?

A

T cells originate in the bone marrow but further develop in the thymus.

54
Q

What do B cells recognize?

A

B cells recognize intact protein antigens, whether they are soluble or pathogen-associated.

55
Q

What do T cells recognize?

A

T cells recognize peptides derived from processed antigens and presented to them by another cell.

56
Q

What is the location of the receptor (antibody) for B cells?

A

The receptor (antibody) for B cells is both on the cell surface and secreted (soluble).

57
Q

What is the location of the receptor for T cells?

A

The receptor for T cells is on the cell surface only.

58
Q

Are there any major differences between B cell subsets?

A

There are subsets reported for B cells, but there are no major differences other than antigen specificity.

59
Q

What is the major subset differentiation in T cells?

A

The major subset differentiation in T cells is between CD4+ and CD8+ T cells.

60
Q

Do B cells undergo receptor mutation during affinity maturation?

A

Yes, B cells mutate their receptor during affinity maturation to improve binding to the antigen.

61
Q

Does affinity maturation occur in T cells?

A

No, affinity maturation does not take place in T cells.

62
Q

What is the nature of the immune response in innate immunity?

A

The innate immune response is broad and does not have memory of an infectious agent, even after repeated infections.

63
Q

What is the nature of the immune response in adaptive immunity?

A

The adaptive immune response improves specificity following repeated infections due to immunological memory.

64
Q

What are some examples of soluble molecules involved in the innate immune response?

A

Soluble molecules involved in the innate immune response include lysozyme, complement factors, cytokines, and chemokines.

65
Q

What are some examples of cells involved in the innate immune response?

A

Cells involved in the innate immune response include macrophages, neutrophils, eosinophils, and natural killer (NK) cells.

66
Q

What are some examples of soluble molecules involved in the adaptive immune response?

A

Antibodies and cytokines are examples of soluble molecules involved in the adaptive immune response.

67
Q

What are some examples of cells involved in the adaptive immune response?

A

Cells involved in the adaptive immune response include T cells and B cells.

68
Q

Do the innate and adaptive immune systems communicate with each other?

A

Yes, the innate and adaptive immune systems do communicate with each other.

69
Q

Can you provide examples of how innate and adaptive immunity interact?

A

Antibody Fc domains can activate the complement cascade, which is part of the innate immune response.
Phagocytes can process and present antigens in MHC class II context, facilitating the adaptive immune response.
Natural killer (NK) cells possess receptors that bind to the Fc domain of antibodies, allowing them to target specific antigens.

Foundations of health and disease (45 decks)

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