Chapter 4: Major histocompatibility complex I and II

Chapter 4: Major histocompatibility complex I and II

Competitive ELISA

The fourth type of ELISA is competitive ELISA. As the name suggest there is going to be a competition between someone. Now let’s see between whom is this competition exactly going to be.

Competitive ELISA

Immunoglobulin A and IgA deficiency mnemonic

IgA occurs as a monomer in the bloodstream and as a dimer when secreted (linked by the secretory component or a J chain attained from epithelial cells before secretion).

IgA is secreted onto mucosal surfaces (gastrointestinal, genitourinary, and respiratory) to block attachment of pathogens to mucous membranes.

Mnemonic: “ABCDE”
A: Alone (Monomer)
B: in Blood
C: Component (Secretory component) or Chain (J chain) makes
D: Dimer
E: in Epithelial surfaces

What happens in IgA deficiency? Mnemonic!

Sandwich ELISA

To remember this type of ELISA, imagine a sandwich! The antigen is the filling and the antibodies are the yummy bread. Hungry, aren't you?

Sandwich ELISA

Indirect ELISA

Indirect ELISA is used for detection of a particular antibody in a given sample. Most of the HIV diagnosis kits use indirect ELISA principle.

Indirect ELISA

Direct ELISA

Direct ELISA is performed by attaching the sample antigens on a surface (walls of wells) then a specific antibody is applied so that it can bind to its corresponding antigen.

Direct ELISA

ELISA: Enzyme Linked Immuno Sorbent Assay

ELISA: Enzyme Linked Immuno Sorbent Assay

From pregnancy detection kits to HIV diagnosis it is ELISA which gives us appropriate results.  

Though ELISA has got a complex name, the way in which it diagnosis is really simple!

ELISA is performed in special micro titre plates which has wells in which we add our sample and then perform ELISA.

There are 4 types of ELISA:

- Direct

- Indirect

- Sandwich
- Competitive

We’ll explain them one by one over the next few blogs. So stay tuned! :)

Written by Komal M. Kadam

Policemen of our body

Just like policemen save us from criminals, immune cells save our body!

T cell

Nitric oxide

Platelets, Endothelium and Nitric oxide

Interleukin 1 mnemonic

Interleukins
The name (IL) followed by a number (for example IL-l or IL-2) was coined in an attempt to develop a standardized nomenclature for molecules secreted by, and acting on, leukocytes.

IL-1: It is an acute phase reactant synthesized by macrophages contributing to the acute inflammatory response, including fever, leukocyte recruitment, adhesion molecule activation, and stimulation of further chemokine production.

Mnemonic: One makes you burn like the sun.

We are writing a book, Immunowesome and it will be available for download soon! Stay tuned :D

Where do B cells and T cells reside in the lymph nodes and spleen?

Ever wondered where do these tiny little cells live in your body?
They live in organs called lymph nodes and spleen!

T cells and B cells in lymph node and spleen

Structure of antibody

Structure of antibody (Old image + notes)

Why are transplanted organs rejected?

What happens in graft rejection?

How superantigens work

Wanna learn about a super villain today?

Antigen presentation

Enzyme-linked immunosorbent assay (ELISA) simplified

Why was the ELISA test sad after a negative result? Because it is very sensitive! HAHAHA! Sensitive, get it? HAHAHA!

Cell wall of gram positive and gram negative bacteria mnemonic

Cell wall of gram positive and gram negative bacteria mnemonic

Education of T lymphocytes

Education of T lymphocytes

Maturation of a wanna be T cell

When you are a kid at home, you wanna be something, but you don't know what. You are at the pro-something stage of your life. You could be a pro-science or a pro-arts.

Similarly, in the bone marrow, pro T cells know they wanna be a T cell but they don't know which one. Pro T cells are double negative, that is, CD4 -ve and CD8 -ve.

Pro T cell

Stages of delayed type of hypersensitivity simplified

Type IV or delayed type of hypersensitivity is a bit different because unlike type I & type II hypersensitivity which is mediated by antibodies, type IV is mediated by T cells.
The whole response is directed by chemokines and cytokines released by antigen-stimulated Th1 cells.

This is how it goes..

An antigen tries to sneak into your immune system but it is caught by the very efficient antigen presenting cell (APC).
The APC gobbles the antigen up, processes it & presents it on MHC class II molecules.
APCs are transported regional lymph nodes where Th1 cells are activated by the antigen.

The sensitization phase takes 1-2 weeks, and it this period, Th cells are activated and clonally expanded.
(An army of Th cells is being made *evil laugh*)

Everybody is living happy now until the same antigen tries to sneak into your immune system..

It is caught by the very efficient antigen presenting cell (APC), again.
The APC does the usual, gobbles the antigen up, processes it & presents it on MHC class II molecules.
This uptake, processing, and presentation of the antigen by local APCs is the first phase of delayed type of hypersensitivity.

Antigen presentation - First phase of the delayed type of hypersensitivity response

Thymus dependent activation of B lymphocytes simplified

"Activation makes the B cell a hero & bestows new responsibilities to it."

Thymus dependent activation of B lymphocyte