Biochem revision - Week 10 Immune System

Question 1

What are the two branches of the immune system?

Answer 1

The immune system consists of cellular and chemical components with two branches:

1. Innate (non-specific)
2. Adaptive (specific, ‘remembers different pathogens)

Question 2

What are the three physical barriers to foreign microbes?

Answer 2

1. Skin cells or mucus traps microbes
2. Tears and saliva contain antibodies
3. Micorbes are removed by shedding skin, coughing, vomiting, diarrhea or flushing bodily fluids urine/tears

Question 3

What are the 3 types of innate immune cells? Which is the most abundant in the blood?

Answer 3

• Monocytes/Macrophages (3-9% of blood)
  Monocytes leave the blood and form macrophages in tissue that consume/engulf dead cells through phagocytosis
• Neutrophils (60% of blood)
  Neutrophils also use phagocytosis but they are the most RAPID RESPONDER to infection
• Natural Killer cells (1-6% of blood)
  Natural Killer cells destroy virus-infected or cancerous cells. They do this by producing proteins, such as ‘CYOKINES’ that kill infected/transformed cells

NEUTROPHILS are the most abundant

Question 4

What cell category belongs to the ‘adaptive’ or ‘specific’ immune system?

Answer 4

Lymphocytes are the cells of the adaptive immune system

Question 5

What is a microbe?

Answer 5

A ‘microbe’ is a collective term for bacteria and viruses

Question 6

What are complement proteins and what do they do?

Answer 6

Complement proteins are proteins made in the liver that can bind to antibodies or patterns on microbes or dead cells are RECRUIT phagocytes to the site via chemical gradients

This initiates a complement cascade

Question 7

How do the two branches of immunity communicate with each other?

Answer 7

Dendritic cells or ‘antigen presenting cells’ digest/process the antigen part of foreign bodies and present these to cells of the adaptive immune system (T and B cells)

The adaptive immune cells then circulate back and produce more of theses cells to attack the foreign agent

Question 8

What are the two cells (that we covered) of the adaptive (specific) immune system?

Answer 8

1. T-cells (branch of cell-mediated immunity)

T-cells release CYTOKINES to kill virus infected cells or tumors

2. B-cells (branch of humoral immunity)

B-cells differentiate into plasma cells and produce ANTIBOIDIES that trap an infected cell and trigger other immune cells to then destroy the cell

Question 9

What are the two types of T- cells?

Answer 9

a) Helper T-cells are considered regulatory T-cells because they recruit other T and B cells to the site of infection/damage

b) Cytotoxic T-cells are the highly efficient specific killers that release cyotokines. They recognize antigens on the surface of damaged/infected cells or tumors

Question 10

What are the four different measurements of immunity?

Answer 10

a) Self-reported illness

b) Concentrations of immune cells (T, B, neutrophils)
The activation or suppression of a specific cell type
Measure of immune function

c) Release of molecules reflecting an immune response such as antibodies or enzymes

d) In vivo immunity i.e measuring how antibody responses to a vaccine or how fast a wound is cleare3d

Question 11

What is the ‘open-window’ hypothesis?

Answer 11

After a bout of moderate or intense exercise, the concentration of immune cells (leucocytes) decreases below the resting value, leaving the person more suspectable to infection 1-2 hrs post exercise

Although, this theory is controversial because in animal testing, leucocytes have been found in other tissues/organs

Question 12

What are the mechanisms that drive immune cell mobilization? Which immune cell is primarily mobilized?

Answer 12

Sympathetic drive/vasoconstriction and [adrenaline] DEMARGINATE immune cells into peripheral blood

T-cells and natural killer cells are preferentially mobilized

Question 13

What are the categories of the innate immune system?

Answer 13

Cell mediated:
Monocytes/Macrophages consume microbes and dead cells
Neutrophils (kill virus and bacteria)
Natural killer cells (kill virus infected cells and cancerous cells)

Humoral: Complement proteins bind to antibodies, patterns on microbes or dead cells, forming protein complexes that recruit phagocytes

Question 14

What metabolic pathway does a T-cell use when encountering a virus/bacteria?

Answer 14

A T-cell will switch from mitochondrial respiration to rely on glycolysis for rapid ATP generation

Question 15

What are some effects of chronic exercise on immunity?

Answer 15

Repeated recirculation of immune cells can:

• Decreased # of infections and severity of infections
• Increased antibody production
• Better response to vaccine
• Faster wound healing
• Increased surveillance of cancer cells

Question 16

What is the infection risk like on the continuum of exercise intensity? ( Sedentary behavior, Moderate exercise, and High intensity exercise)

Answer 16

Sedentary behavior results in a slight increased infection risk

Mod. exercise lowers the infection risk

High intensity exercise can greatly increase one’s risk of infection

Question 17

Why do some researchers argue that arduous exercise bouts/periods of intensified training can impair immune function? (Theory)

Answer 17

One theory is that immune cell activation might become impaired after heavy exercise as the oxygen and nutrient demands of the cell exceed its metabolic capacity. Metabolism is also unable to ‘shift’ to produce more ATP

Question 18

What is ‘immunosurveillance’ and how can it be upregulated?

Answer 18

Immunosurveillance is the increases in the circulation of immune cells which can be upregulated through bouts of exercise.

Regular exercise can also improve immunity decline with age, as well as those with autoimmune, cardiovascular, neurological and metabolic illnesses