MAJOR HISTOCOMPATIBILITY COMPLEX & HEAT SHOCK

PROTEININ CHICKEN

Dr. S. SivaramakrishnanMVM 15032(PSC)

Department of Poultry Science

Madras Veterinary College

MHC (Major histocompatibility complex)

A large cluster of linked genes located in some chromosome of chicken, encode for MHS and relate to immune response, immune regulation and cell-cell recognition.

History • MHC is a group of highly conserved genes defined by its

influence on tissue graft acceptance. • MHC was discovered in the 1930s by Peter Gorer in his

pioneering studies of antigenic responses to transplanted sera by inbred mouse strains (Gorer 1936)

• The chicken was the second animal species in which the MHC was identified (Schierman and Nordskog, 1961)

• Chicken MHC has been designated as the B complex because of its linkage with the B blood group (Briles et al., 1950)

MHC function

MHC Peptides

Pathogen

T Cell

Present antigen to initiate immune response with a phenomena

known as MHC restriction Endogenous Ag is presented to CD8+ T cell by MHC class Ⅰ

molecule Exogenous Ag is presented to CD4+ T cell by MHC class Ⅱ

molecule Participant in both humoral and cell-mediated immunity Act as antigen presenting structures

Biological function of MHC

Properties of MHC1. MHC is polygenic it contains several

different MHC class I and MHC class II genes - different ranges of peptide-binding specificities.

2. MHC is highly polymorphic – multiple variants of each gene within the population as a whole.

– Class I MHC genes (B-F)• Glycoproteins expressed on all nucleated cells• Major function to present processed Ags to TC

– Class II MHC genes (B-L)• Glycoproteins expressed on M, B-cells, Monocytes• Major function to present processed Ags to TH

MHC Classes

– Class III MHC genes• Products that include secreted proteins that have immune

functions. Ex. Complement system, inflammatory molecules - Class IV MHC genes (B-G)• expressed on erythrocytes and other cells such as liver cells, bursal and

thymic lymphoblast and stromal cells.

• The class IV MHC is involved in antibody response, which is supposed to

involve B cell repertoire and the B cell antigen recognition and binding

• The other unique MHC linked gene in the avian, is the Rfp-Y that is recognised by DNA restriction fragment pattern (Rfp) of the MHC class I, II and IV genes in one MHC haplotype

1

3

2MHC-encoded -chain of 43kDa

Structure of MHC class I molecules

3 domain & 2m have structural & amino acid sequence homology with Ig G domains Ig GENE SUPERFAMILY

2m

2-microglobulin, 12kDa, non-MHC encoded, non-transmembrane, non covalently bound to -chain

Peptide antigen in a groove formedfrom a pair of -helicies on a floor of anti-parallel strands

-chain anchored to the cell membrane

2

1

and a -chain of 29kDaMHC-encoded, -chain of 34kDa

2

1

Structure of MHC class II molecules

and chains anchored to the cell membrane

2 & 2 domains have structural & amino acid sequence homology with Ig G domains Ig GENE SUPERFAMILY

No -2 microglobulinPeptide antigen in a groove formed from a pair of -helicies on a floor of anti-parallel strands

MHC and immune responseMHC molecules interact with both the foreign

antigen and with complementary structure of other immune cells, thereby generating an immune response that is specific for the inducing antigen

The T-/B-cell co-operation necessary for antibody production and for the generation of germinal centres in the spleen requires identity at the MHC

Interaction of APCs and T cells, evaluated by the in vitro proliferation of T cells in response to specific antigen in the presence of APCs, is also MHC-restricted.

The B-F/B-L antigens are the restriction elements for all of these cellular interaction phenomena.

The MHC effects on genetic control of immuno-responsiveness, either due to restriction element or through specific MHC-linked immune response genes.

Antibody production against a variety of antigens, such as immune response to synthetic polypeptides, is linked to the chicken MHC (Gunther et al., 1974)

Complement proteins are extremely important in the immune reaction as a means to destroy invading pathogens.

The levels of total serum haemolytic complement have been associated with the MHC in chickens.

MHC and disease resistance MHC – resistance to a specific disease concerns Marek's disease (MD),

a herpesvirus-induced lymphoma. Using MHC recombinants to the B-F/B-L region, partial MHC control

has been mapped. The MHC is associated with MD-related traits of incidence of tumour

formation, mortality and transient paralysis induced by MDV. The haplotype B21 conveys MD resistance to many different genetic

backgrounds. Variation in response to MDV by sublines that are identical at the B

locus, however, illustrates the influence of non-MHC genes on response to MD (Bacon L.D. - 1987)

Selected diseases for which an association of resistance or severity is found with the chicken MHC

Type of disease DiseaseNeoplastic diseases (virally induced) Marek's disease neoplasia

Marek's disease transient paralysis

Rous' sarcomas

Lymphoid leucosis

Bacterial diseases Staphylococcus aureus

Fowl cholera (Pasteurella multocida)

Salmonella enteritidis

Parasitic diseases (coccidiosis) Eimeria tenella

Eimeria acervulina

Autoimmune diseases Autoimmune thyroiditis

Chicken MHC and production traits Economically important traits, such as juvenile and adult

mortality, body weight, fertilization rate, embryonic mortality, hatchability and egg production are influenced by MHC genotype (Bacon L.D. - 1987)

Several independent studies have shown that long-term selection for egg production traits and disease resistance have significantly altered MHC allelic frequencies (Gavora et al., 1986)

From these selection studies, B2 and B21 appeared to show overall beneficial associations with economic traits in chickens.

• Birds which were aneuploid (trisomic) for the MHC-bearing chromosome were used to map the MHC to microchromosome 16 and to examine the effects of MHC gene dosage on several biological systems.

Selected production traits for which an association with the MHC is found

Production traits

Body weight

Juvenile survival

Adult survival

Egg production

Hatchability

Embryonic mortality

Fertilization rate

Applications of MHC manipulation to the poultry industry

Differences between MHC types can be identified by using serological blood typing or by restriction fragment length polymorphism analysis of DNA and can be utilized in several ways by the breeding industry.

An MHC (or B blood group) allele can be used as a pedigree marker, if it is unique to a genetic line within a company, and thus can identify that line and any accidental crosses made with it.

MHC manipulation is to alter the frequency of alleles in the population to improve associated traits such as disease resistance, immune response and production traits (Lamont, 1989).

Future industrial applications of MHC manipulation may include alteration of the gene copy number in individual animals by use of natural variation or genetic engineering (Bloom et al., 1988).

HEAT SHOCK PROTEINS(HSP)

History• HSP Discovered in 1962 Ferruccio Ritossa (1936-

2014)• chromosomes of salivary glands in Drosophila

melanogaster larva• Heat shock proteins are highly conserved molecules

that are present, and can be induced, in all eukaryotic and prokaryotic species, including plants

Functions • The primary function of these proteins is to govern the folding

and refolding mechanism of native and stress denatured proteins. • Unfolded polypeptides, prevent their aggregation and thereby,

potentiate the folding process. • Hsps are also involved in diverse cellular roles such as protein

assembly, translocation and degradation. • Hence these proteins are the essential determinants of protein

quality control in cell.

Classification Based on their molecular mass and function, HSPs are classified into six families namely;

1. Small Heat Shock Proteins (sHsp/Hsp20), 2. Hsp40 (J-class proteins), 3. Hsp60 (Caperonin), 4. Hsp70, 5. Hsp90, 6. Hsp100 proteins

Tempenviron

Tempcell

Folded Proteins

Unfolded Proteins Aggregates

Loss of ProteinFunction

Networkfailure

Death

CellNeed for HSP

HSP Synthesis• Transcription of HSP genes is mediated by the interaction

of heat shock factor (HSF)• Chickens, four HSFs have been identified• HSF1 and HSF2 are ubiquitously expressed and conserved.• HSF1 – physiological and environmental stress • HSF2 – mostly induced during differentiation and early

development.

• HSF1 - present in the cytoplasm as a latent monomeric molecule that is unable to bind to DNA.

• When exposed to stress, an intracellular flux of newly synthesised non-native proteins activates HSF1 (hyperphosphorylated)

• HSF1 is converted to phosphorylated trimers that have the capacity to bind DNA, and which translocate from the cytoplasm to the nucleus.

• HSF2 has the characteristics of a temperature-sensitive protein; it is inactivated when exposed to raised temperature, and sequestered to the cytoplasm, and is thereby prevented from interference with HSF1 activity in stressed cells.

Major family Intracellular localisation Intracellular function

Hsp27 Cytoplasm/nucleus Actin dynamics

Hsp32 Cytoplasm Haem catabolism, antioxidant of properties

Hsp40 Cytoplasm/nucleus Regulates the activity of Hsp70; binds non-native Proteins

Hsp47 ER Processing of pro-collagen; processing and/or secretion of collagen

Hsp60 Mitochondria Bind to partly folded polypeptides and assist correct folding. Assembly of multimeric complexesHsp70

HSP Location and Function

Hsp70 Cytoplasm/nucleus Bind to extended polypeptides. Prevent aggregation of unfolded peptides. Dissociate some oligomers. ATP binding. ATPase activity. Hsp70 downregulates HSF1 activity

Hsp90 Cytoplasm Bind to other proteins. Regulate protein activity. Prevent aggregation of refolded peptide. Correct assembly and folding of newly synthesised protein. Hsp90 assists the maintenance of the HSF1 monomeric state in non- stressful conditions.

Hsp110 (human)

Nucleolus/cytoplasm Thermal tolerance

Hsp105 Cytoplasm Protein refolding

HSPs in antigen presentation by MHC class I/II molecules

HSPs and autoimmunity • HSPs, particularly Hsp60 and Hsp70, are highly immunogenic

capable of inducing antibody production and T cell activation. • The antibodies and T cells against bacterial Hsp60 and Hsp70

also recognize chicken Hsp60 and Hsp70 respectively, as a result of cross reactivity.

• These anti-Hsp60 and anti-Hsp70 anti- bodies and T cells injure tissues and cause inflammatory reactions. Thus, Hsp60 and Hsp70 have been implicated in the pathogenesis of a number of autoimmune diseases and inflammatory conditions.

HSP influenced on immunity

HSP on specific immunity

HSP in Disease resistance • Zulkifli et al., 1994a and Liew et al., 2003. They reported that

stress due to neonatal feed restriction can improve resistance to marble spleen disease and infectious bursal disease in feed restricted chickens in comparison to those fed ad libitum.

• Solemani et al., 2012 stated that 60% feed restriction and 60% feed restriction plus quercetin (1500mg/kg) from day 4 to 6. Resulted that both the groups had significantly lower Salmonella enteritidis colonization and lower HSP70 expression then that of controlled chickens

• Zulkifli et al., 2003. conducted a trial on 36 days old birds was administered 10 times the normal dose of live IBD vaccine. After heat exposure , the Feed Restricted Heat treatment birds had higher HSP70 density and weight gain and lower bursal histological score then their heat treatment and control birds. They concluded that Feed Restricted Heat treatment could improve weight gain and resistance to Infectious Bursal Disease in male broiler chickens

HSP in Heat tolerance• Yahav et al. (1997) reported that exposure to acute heat stress

resulted in enhanced synthesis of heat shock protein. Synthesis of heat shock protein induced to a lesser extent in tissues of broiler chicken, which acquired improved heat tolerance, than in tissues of control chickens.

• Azim (2012) observed that exposing chicks to heat treatment at 40ºC for 4 hours daily during the first 14 days. He reported to improve the heat tolerance of broilers through heat treatment during the first two weeks.

• Yahav and McMurtry (2001) found that thermal conditioning of chicks results in improvements in performance and heat tolerance at marketing age. He resulted thermal conditioning is growth retardation followed by an immediate compensatory growth period, which resulted in complete compensation for the loss of weight gain, and lead to higher body weight of the conditioned chickens at 42 day of age.

Conclusions• MHC and HSP are highly conserved genes. MHC mainly acts on immune

regulation. • HSP are extremely potent molecules, importance for physiological and

immunological process is indicated by the high degree to which their structure and function are phylogenetically conserved.

• Through the gene mapping to develop the disease resistance breeds. • In native chicken like Aseel are more disease resistant due to the highly

expression of MHC genes compared to commercial chicken. Likewise HSP in native chickens highly expressed in stress conditions compared to commercial chickens so that mortality also low in native chickens.

• Both MHC and HSP genes used to increase the production traits of the chicken.

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