Major histocompatibility complex

1. MHC
19 July 2021 Abhijit Debnath BP605T and Biotech Unit-1 1
CO1.1
Noida Institute of Engineering and Technology
(Pharmacy Institute) Greater Noida
Abhijit Debnath
Asst. Professor
NIET, Pharmacy
Institute
Unit: 3
Subject Name: Biotechnology
(BP605T)
Course Details
(B. Pharm 6th Sem)

2. 19 July 2021 Abhijit Debnath BP605T and Biotech Unit-1 2
 Antigen-presenting cells
 Major Histocompatibility Complex (MHC)
 Structure Of MHC
 MHC Working Pathway
 MHC Associated Genes
 Similarities Between MHC Class I & MHC Class II
 Differences Between MHC Class I & MHC Class II
 Cytokines
 Interleukins (IL)
 Interferons (IFN)
 Chemokines
Lecture 20
Noida Institute of Engineering and Technology
(Pharmacy Institute) Greater Noida

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ANTIGEN-PRESENTING CELLS
 Antigen-presenting cells (APCs) are a group
of immune cells that mediate the cellular
immune response by processing and
presenting antigens for recognition by
certain lymphocytes such as T cells. Classical
APCs include dendritic cells, macrophages,
Langerhans cells and B cells.
MHC

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ANTIGEN-PRESENTING CELLS

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MAJOR HISTOCOMPATIBILITY COMPLEX
 Major histocompatibility complex (MHC), group of
genes that code for proteins found on the surfaces of
cells that represent antigen to T cells for intracellular
recognition & discriminate between self (our cells
and tissues) and nonself (the invaders or modified
self).
 Another function of the major histocompatibility
complex is tissue allorecognition, an important factor
in the prevention of successful organ transplantation.
 In human beings the complex is also called the
human leukocyte antigen (HLA) system.
 There are two major types of MHC protein
molecules— MHC class I and MHC class II.
The B-cell receptors (antibodies) can recognize
antigens and on their own, while T-cells can do so
through the mediation of MHC.
MHC

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STRUCTURE OF MHC
MHC Class I molecules are found on almost all the nucleated cells of
the body.
MHC Class I molecules are found on almost all Antigen Presenting
cells like macrophages, B cells and dendritic cells.
MHC Class I MHC Class II

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MHC WORKING PATHWAY
MHC Class I MHC Class II

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 In humans, the MHC proteins are encoded by a cluster of genes located on chromosome 6.
 The MHC gene family is divided into three subgroups: MHC class I, MHC class II, and MHC class III.
 Among all those genes present in MHC, there are two types of genes coding for the proteins MHC class I molecules and
MHC class II molecules that directly involved in the antigen presentation.
MHC ASSOCIATED GENES

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SIMILARITIES BETWEEN MHC CLASS I & MHC CLASS II
 Both are synthesized in rough endoplasmic reticulum
 Both are found on the surface of APC surface
 Both are encoded by genes in HLA locus
 In both class I and class II, expression of genes is co-
dominant
MHC Class I MHC Class II

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DIFFERENCES BETWEEN MHC CLASS I & MHC CLASS II
MHC Class I MHC Class II
MHC Class I MHC Class II
Peptide binding
domain
alpha1, alpha2 alpha1, beta1
Amino Acids Have 8-10 amino acids Have 13-18 amino acids
Distribution All nucleated cells All Antigen Presenting cells like macrophages, B
cells and dendritic cells.
CD4 binds to the
b2 region
a1 and a2 domains a1 and b1 domains
Present antigen to cytotoxic T cell lymphocytes Present antigen to helper T cell lymphocytes
Binding site for T
cell co-receptor
CD8 binds to the a3 region CD4 binds to the b2 region
Binds with Bind endogenous antigens synthesized in a cell Binds exogenous antigens
Acts Presence of foreign or over-abundant antigens
targets cell for destruction
Presence of foreign antigens induces antibody
production, and attracts immune cells to area
of infection
Chain Has no invariant chain Has invariant chain

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Cytokines
Small soluble molecules

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CYTOKINES
* Autocrine mean cytokine acts on the same cell and para line means cytokine acts on the nearby cells
 Cytokines are produced and secreted by wide variety of cells
 They act as Intercellular mediators hormone-like substances that
means they are signaling molecules
 Cytokines are soluble molecules and some of them are membrane
bound molecules
 Chemically they can be protein or glycoprotein
 The molecular mass is less than 30 kDa
 Cytokines have short half-life
 Mostly cytokine act over a short distance (autocrine or paracrime) *
 Cytokines are effective at low concentrations this is because of the
specific high affinity cytokine receptors

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CYTOKINES
 Cytokines Strom in Covid-19

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Important cytokines which are involved in signaling between cells of the immune system are
 Interleukins (IL)
 Interferons (IFN)
 Chemokines
CYTOKINES

15.  Interleukins are a subset of a larger group
of cellular messenger molecules called
cytokines, which are modulators of cellular
behaviour.
 Like other cytokines, interleukins are not
stored within cells but are instead secreted
rapidly, and briefly, in response to a
stimulus, such as an infectious agent.
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INTERLEUKINS (IL)

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INTERLEUKINS (IL)
Courtesy: Frank Lectures

17.  A virus-infected cell releases interferons causing nearby cells to heighten their anti-viral defenses.
 Interferons (IFNs) are proteins made and released by host cells in response to the presence of pathogens such as
viruses, bacteria, parasites or tumor cells.
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INTERFERONS (IFN)
 IFNs belong to the large class of proteins known as cytokines, molecules
used for communication between cells to trigger the protective
defenses of the immune system that help eradicate pathogens
 They also allow for communication between cells to trigger the
protective defenses of the immune system that eradicate pathogens or
tumors.
 ϒ-IFNs are produced by NK cells that activate macrophages (Type II IFNs) NK cells ϒ-IFNs Macrophage activation
 Whereas, α and β IFNs are produced by virus infected cells that activate NK cells. (Type I IFNs) Virus infected cells α, β
IFNs NK cellactivation.

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Courtesy: Frank Lectures
INTERFERONS (IFN)

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TYPES OF INTERFERONS

20.  Chemokines, are a family of small, secreted, and structurally related cytokines with a crucial role in inflammation and
immunity.
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CHEMOKINES
 They are also key mediators of cancer
related inflammation being present at
tumor site for pre-existing chronic
inflammatory conditions but also being
target of oncogenic pathways
 Play role in determining the
composition of tumor stroma, they
were found able to directly affect
cancer cell proliferation and metastasis

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Courtesy: Frank Lectures
CHEMOKINES

22. THANK YOU