Exam 2- Lecture 4: IgG Classes & Subclasses

What are the IgG, IgD, & IgE valence?

2

What is the IgA valence?

4

What is the IgM valence?

10

What are the implications for the valences?

Enhanced collective affinity for multivalent antigens

What are the aspects of IgG?

• % in serum: 75% (most abundant)

• Opsonization: yes

• Complement: yes

• Leukocytes activation: neutrophils & NK cells

• Placental passage: yes

What are the aspects of IgA?

% in serum: 15%

What are the aspects of IgM?

% in serum: 10%

Complement activation: yes

What are the aspects of IgE?

• % in serum: 0.004% (least abundant)

• Leukocytes activation: mast cell & basophils

What are the aspects of IgD?

% of serum: 0.2%

What is the medicated function of FcgR?

Opsonization; ADCC

What is the medicated function of FcRn?

Placenta transport

What is the medicated function of FceR?

Allergic rxns

What are the variable light chain & constant heavy chain connected by?

Disulfide bonds

What are the IgG subclasses?

• IgG1

• IgG2

• IgG3

• IgG4

What is the antibody response to proteins?

• IgG1: ++

• IgG2: ±

• IgG3: ++

• IgG4: ++^e

What is the antibody response to polysaccharides?

• IgG1: +

• IgG2: +++

• IgG3: ±

• IgG4: ±

What is the antibody response to allergens?

• IgG1: +

• IgG2: -

• IgG3: -

• IgG4: ++

What is the antibody response to ADCC/FcgR?

• IgG1: +++

• IgG2: +

• IgG3: +++

• IgG4: -

What is the antibody response to C1q binding?

• IgG1: ++

• IgG2: +

• IgG3: +++

• IgG4: -

What is the relative abundance for IgG1, IgG2, IgG3, & IgG4 (%)?

• IgG1: 60 (most abundant)

• IgG2: 32

• IgG3: 4

• IgG4: 4

What is the half-life (days) of IgG1, IgG3, IgG3, & IgG4?

• IgG1: 21

• IgG2: 21

• IgG3: 7 (shortest t1/2)

• IgG4: 21

What do all IgG subclasses have?

• Molecular mass 140-180 Kd

• Are held together by disulfide bonds

• Can cross the placenta via neonatal Fc receptors (FcRn)

What are IgG1s?

Primary antibody response to protein antigens; it is most abundant gamma subclass in blood

What are IgG2s?

Critical for response to infections from polysaccharides encapsulated bacteria

What are IgG3s?

Shortest half-life amongst IgG subclasses in blood circulation

What are IgG4s?

Do not fix complement & lack sufficient ADCC activities, therefore do not exhibit direct killing functions

What are the aspects of Herceptin?

• trastuzumab

• IgG1

• Neutralization ADCC & complement

What are the aspects of OPDIVO?

• nivolumab

• IgG4

• Neutralization

What do immune cells do?

Kill by 1 by 1 in specific manner

What are Fc gamma receptors?

On certain WBCs

What happens with the tumor cell connected w/ the T cell?

Turns off & kills the T cell

• Need to block the symbol

What does nivolumab do?

• T cell is still on & can kill cancer cells

• Tumor cell blocked from connecting