Immunoglobulin

By- Akshay Singh

Introduction

• Immunoglobulins, also known as antibodies, are glycoprotein molecules produced by plasma cells (white blood cells).

• They act as a critical part of the immune response by specifically recognizing and binding to particular antigens, such as bacteria or viruses and aiding in their destruction.

B-cell• B-cells are types of lymphocytes about 30% of circulating

lymphocytes.• B-cells in fetal liver→ bone marrow → germinal center of

lymph nodes → spleen → and finally comes out in pier patches.

• B-cell have exposed some antigens they have become active & they fight the antigen and they become a memory B-cell.(it have longer life span).

• It have 3 phases • No IgM on the surface/Bone marrow[B-cell] In the bone marrow they will start form the stem cell then

will have pre B-cell and then we have B-cell.• Actually 2 phases stem cell should not be called “B-cell”

IgM & IgD

• IgM act`s as a receptor for antigen & these B-cells are activated.

• The IgM & IgD are activating of B-cell.

• Plasma cell are converted into memory cell & they live on for decades.Decades means memory cell.

• IgG released from the B-cell into the blood stream.• And it`s work to re-exposure to that pathogen &

quickly make it work and produce the IgM.

The function of B-cell are types:-• (a) To make & release the immunoglobulin.• [this is Humoral response]• (b)APC (antigen presenting cell) :- macrophage & APC

dendritic cells are APC they do at to activate immune system.

• Hyper-gamma-globulinemia when B-cell not become active IgD & IgM works stops.

• B7 & CD28 are the proteins that makes activated to the T-cells.

• CD40 & CD40L this so important it may cause a class switching.

• IL2:- it activates T-cell itselfs & also activate B-cell.

• IL4:- it makes the proliferation of B-cell and it makes the B-cell copies.(proliferation means making simply copies of clone so it`s called clonal expression.)

• It is also work on class switching towards IgE (IL4,CD40,CD40L) is involved in allergies.

• IL5:- it form IgA that also help in class switching but it does one more thing is differentiation.(when cell become more and more specification)

Structure of immunoglobulin

• Have a common structure with four polypeptide chains.• The heavy chain is chromosome no.14 & they are called

isotypes.• Light chain are 2 types:- K (60% more chr.2) λ(30% less chr.22)• The disulphide bonds joining the antibody heavy chains are

located in a flexible region of the heavy chain known as the hinge region.

Allealic exclusion of immunoglobulin

• When the B-cell is maturing in the bone marrow.(the stem cell helps to make B-cell mature)

• Maternal is expressed and paternal is silence.

• Conclusion:-1 B-cell will only expressed immunoglobulin that have gene coming from father or mother.

Gene Regions

• In light chain we have V,D,J gene regions.• In heavy chain Cμ, Cδ, Cγ₃, Cγ₁ , Cγ₂a , Cγ₂b , Cε

, Cα• ε :-abslone• “V” only attached with “D” not with “J”.

RSSS :- recognition signal sequence

• We have heptamer(7) and nanomere(9) in both of end points of “V” & “J”.And in between of them we have base pairs.

• RAG :- re-combinase activation gene. (it helps to remove this loop from the gene this process is called hair pining rule).

TDT :- add or remove the nucleotide

This PN nucleotide takes place only in between of D & J.

• Follicular dendritic cell:- The dendritic cell which is

present in the rest of the body or tissue, skin (they not do this) this is spetiality of it.

•Now B-cells are in lymphnode because it becomes active.

•Point mutation :- They change the structure of next immunoglobulin.

•After SHM create a new B-cell because they keep proliferation because they are active.

(1).Halmanth attacks in IgE(2).Virus attacks IgM,IgG,Ig1(3).Bacteria attacks IgG3.

Thank you