Immunological response

Question 1

What is an antigen?

Answer 1

Is a substance that evokes the production of antibodies.

Question 2

What is an antibody?

Answer 2

Is a receptor that binds to a specific antigen, to
destroy or neutralize a foreign invader or substance.

Question 3

What is phagocytosis?

Answer 3

A process by which phagocytes engulf other
cells or particles. The foreign substances are destroyed
through different steps.

Question 4

What is a B cell?

Answer 4

A lymphocyte that expresses membrane-bound antibodies
- plasma cells
- memory cells

Question 5

What is a T cell?

Answer 5

T cell: A lymphocyte that expresses a T-cell receptor, CD3, and CD4 or
CD8. Several distinct T-cell subpopulations are recognized.

Question 6

What is an NK cell?

Answer 6

A class of lymphocytes that do not have T- or B-cell receptors
- kill tumor cells
- express cell-mediated cytotoxicity

Question 7

What is a neutrophil?

Answer 7

Circulating, phagocytic cells that are involved early in the
inflammatory response
- cell-mediated cytotoxicity

Question 8

What is a monocyte?

Answer 8

Circulates in the bloodstream, migrate into tissues and
differentiate into macrophages.

Question 9

What is a macrophage?

Answer 9

Are dispersed throughout the body
-phagocytic cell
-tissues (fixed macrophages)
-motile

Question 10

What is a dendritic cell?

Answer 10

Phagocytic cells. Express class II MHC molecules and
co- stimulatory receptors → more potent antigen presenting cells
than macrophages and B cells.

Question 11

What does the dendritic cell do after capturing the antigen?

Answer 11

After capturing antigen in the tissues, the dendritic cells migrate
into the blood or lymph and circulate to various lymphoid organs,
where they present the antigen to T cells.

Question 12

What are the 4 defensive barriers of innate immunity?

Answer 12

Anatomic barrier- Skin, mucous membranes, normal flora
* Physiologic barrier - Temperature, pH, soluble factors
* Phagocytic barrier – Phagocytosis
* Inflammatory barrier – Inflammatory reactions

Question 13

What are the four characteristics of adaptive immunity?

Answer 13

Four characteristic attributes:
* Antigenic specificity
* Diversity
* Immunologic memory
* Self/nonself recognition

Question 14

What are the two important major groups of cells in adaptive immunity?

Answer 14

-Lymphocytes (B cells and T cells)

-Antigen-presenting cells (macrophages, B cells and dendritic cells)

Question 15

What does T helper cells express?

Answer 15

CD4

Question 16

What does T cytotoxic cells express?

Answer 16

CD8

Question 17

What does T regulatory cells express?

Answer 17

FOXP3 transcription factor

Question 18

What is the immune system of the digestive tract called?

Answer 18

The immune system of the digestive tract is called gut-associated
lymphoid tissue (GALT).

Question 19

Mention some organised structures that are part of the immune system but found in the GI tract

Answer 19

organized structures
such as peyer ́s patches (small intestine), mesenteric lymph nodes
(mesentery), follicles (small and large intestine).

Question 20

Can the epithelial cells deliver foreign antigens from the lumen to the
lymphoid tissue?

Answer 20

Yes

Question 21

What is the TLR4 receptor also known as?

Answer 21

TLR4 is known as the LPS receptor (Gram-negative bacteria)

Question 22

What does the TLR2 receptor do?

Answer 22

TLR2 recognizes bacterial lipoproteins and peptidoglycans (Gram-positive
bacteria)

Question 23

What does the TLR receptors do in a healthy individual?

Answer 23

TLR signalling protects the intestinal epithelial barrier and confers
commensal tolerance.

Question 24

What does the TLR receptors do in disease?

Answer 24

aberrant TLR signalling may stimulate diverse inflammatory
responses.

Question 25

How can signals from bacteria be transduced to immune cells?

Answer 25

-Through receptors on epithelial cells such as MHC I and II molecules, and Toll-
like receptors (TLRs), signals from bacteria can be transduced to immune cells.

Question 26

Through bacterial-epithelial cell interactions, probiotics can affect both the
innate and adaptive immune system, mention some.

Answer 26

• When presented by dendritic cells, the probiotic bacteria can modify the
  activity signal in T cells and change the production of cytokines.
• The cytokine pattern produced by macrophages can be changed.
• Up and down-regulation of membrane receptors can affect the signal
  transduction (stronger or weaker).
• Some strains can promote the differentiation of B cells into plasma cells
  and increase the production of secretory IgA.
• Through the activation signal, the probiotic bacteria can affect the number
  of T cell subsets, e.g. regulatory T-cells.
• By changing the composition of the intestinal microflora, probiotics can
  modify the stimulation of the pattern recognition receptors, e.g. more LPS
  in lumen will stimulate an inflammatory reaction.
• By minimizing bacterial translocation, the immune system will be less
  affected by Gram-negative bacteria.
• By stimulating the production of mucus, the epithelial cells will be
  protected from bacterial stimulation.