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MHC I vs MHC II – What is the Difference?

MHC I vs MHC II – What is the Difference?

(MHC I vs MHC II)  Major Histocompatibility Complexes plays crucial role in activating Cell Mediated Immunity in our body. Tc cells and Th cells cannot recognise the peptide alone, they have to be presented peptides on MHC molecules.

MHC molecules present in humans are called HLA – Human Leucocyte Antigen. MHC molecules binds to peptide fragments derived from antigen degradation and display them on the cell surface for recognition by the appropriate T cells. It is also responsible for graft rejection.

MHC class I is present in all nucleated cells. RBCs does not have a nucleus and therefore does not contain MHC class I. It presents the peptide to Tc cells and thus they are involved in clearance of endogenous Ag.

MHC class II is present in Antigen Presenting Cells (APC) such as B cells, dendritic cells, macrophages. It presents the peptide to Th cells and thus they are involved in clearance of exogenous Ag.


Antigen Processing and Presentation | Part I | The Cytosolic Pathway

Antigen Processing and Presentation | Part II | The Endocytic Pathway

Reference book to follow for this topic: Kuby Immunology

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Vaccination and Immunization – Not the Same Thing!

Vaccination and Immunization – Not the Same Thing!

Most probably you guys would know these two terms but I have seen students thinking that they mean the same thing. Vaccination and immunization is not the same thing and let’s understand why.

  • Vaccination

    – From Latin word “vacca” meaning cow was given by Edward Jenner.

Vaccination literally means injection or administration of killed or attenuated Ag (vaccine) that produces the immunity in the body against that particular Ag.

Vaccination results in immunization because the vaccine would stimulate the immune response.

  • Immunization

    – is the process of inducing immunity or stimulating an immune response. It is defined as the process by which the body is prepared to fight against specific Ag or a disease. That means it gives immune resistance to body against specific disease.

So immunization happens after vaccination. But it is never 100% though; sometimes it is possible that the vaccination might not result in immunization due to some reason.

Immunization can be acquired by different means. And vaccination is one of the ways to acquire immunization.

Types of Immunization:

  • Active Immunization:

    is acquired by activating or stimulating the immune system of the body.

A.1 Natural Active Immunization: is acquired by following an infection or a disease.

A.2 Artificial Active Immunization: is acquired by injecting a vaccine.

  • Passive Immunization:

    is produced without challenging the immune system of the body. It is given by Abs or lymphocytes that have been produced by another individual’s immune system.

B.1 Natural Passive Immunization: is acquired before birth by transfer of Abs from mother to fetus through placenta and after birth through breast milk.

B.2 Artificial Passive Immunization: is acquired by injecting Abs in form of vaccine against a specific Ag.

Therefore, vaccination and immunization is not the same thing.

Vaccination results in Immunization OR Immunization is acquired by Vaccination.

I hope this post helps 🙂

To understand more in detail, watch a video on this topic here.