Immunity

Question 1

Opsonins

Answer 1

C3b (a complement)—it marks microbes and increase their susceptibility to phagocytosis.

Question 2

Chemotaxis

Answer 2

Complement fragments С5a, СЗа.

Chemoattractants: attract neutrophils and macrophages to the area where the antigen is present.

Question 3

Natural Killer (NK) Cells

Answer 3

Cytotoxic effects are regulated by MHC class I.

Question 4

Antigen Presentation (Exogenous and Endogenous)

Answer 4

• Exogenous Antigens: Displayed on MHC class II molecules, which activate CD4 T helper cells.
• Endogenous antigens are typically displayed on MHC class I molecules, activate CD8 cytotoxic cells.

Question 5

Paratope

Answer 5

Lock

Question 6

Epitope

Answer 6

Key

Question 7

IgA

Answer 7

• Found in mucosal tissues, prevents colonization by pathogens.
• Found in saliva, tears, colostrum and breast milk
  IgA.
• It contains 2 subclasses; IgA1 and IgA2.
• IgA can be produced as a monomeric form (Serum IgA) as well
  as a dimeric form (Secretory IgA)
• Half-life: 6-7 days.

Question 8

IgD

Answer 8

• Along with IgM they are found on the surface B cells and act as antigen receptor. (Regulating B cell function)
• It also activates basophils and mast cells to produce antimicrobial factors.
• Half-life: less than 3 days (2.8 days)

Question 9

IgE

Answer 9

• Responsible for allergic reactions, it binds to allergens and triggers histamine release from mast cells and basophils.
• Patients with allergic conditions have high concentration of IgE.
• Protect against parasitic worms.
• Half-life: 2-3 days.

Question 10

IgG

Answer 10

It contains 4 subclasses; 1gG1, IgG2, IgG3 and IgG4.

• Representing about 75% of serum antibodies in the body.
• It provides the majority of antibody-based immunity against
  invading pathogens by IgG neutralization, agglutination and complement activation.
• The only antibody capable of crossing the placenta to give
  passive immunity to the fetus.
• Half-life: about 23 days

Question 11

IgM

Answer 11

• Expressed on the surface of B cells as monomer and in a secreted form is pentamer. (Macroglobulin)
• Responsible for the early stage of immunity and rapidly eliminates pathogens, before there is sufficient IgG.
• Half-life: 5-6 days.