Question

Describe the barriers, cells, and proteins involved in the different phases of the immune response

Answer 1

Ans The barrier cells that involved in immune response.

●Phagocytes :- There are two types of phagocytes macrophages and neutrophils.A phagocyte is a cell that is able to engulf the bacteria.The phagocytes engulf bacteria,cell debris ,old cellsor kill pathogens .These are first line immune .

Macrophages :- These are irregular shaped that is amoeboid in nature and come out of blood.Macrophages move through blood tissues and squeeze through capillary walls using pseudopodia.They are called different names depending upon tissues :kuffer cell in liver,histiocytes in connective tissue and alveolar macrophages in lungs.

● Neutrophils:- These cells are activated by chemotaxis from blood tissue to infected tissue.These are granulocytes.These are involved in adaptive immune response also.

●Monocytes:- These are ciculating cells that difderentiates into either a dendritic cells ,which can rapidly attached to areas of infection by signal molecules of inflammation.

●lymphocytes :- Two main lymphocytes present that is T lymphocyte and BLymphocytes

a) B lymphocyte:- B lymphocytes produce antibody that are army of proteins which are produced in body to show response against a pathogen

b )T cell:- T cell does not produce antibody but helps B cell to produce antibody.These provide cell mediated immunity.Body can differentiate self and non self by T lymphocytes.

c) Natural killer cells :- These are lymphocyte that induces apoptosis.The granules of these cells release perforins and granzyme.A perforin is protein that forms pores in membrane of infected cells.A granzyme is a protein digesting enzyme that triggers apoptosis.

Proteins involved in immune response

◆ Cytokine :- It is a molecule that allows cells to communicate wirh each other over short distances .These are secreted into intercellular spaces .

◆ Interferone:- Virus infected cells secretes a protein called interferone which protect non infected cells from further viral infection.These are early induced proteins .Macrophages have receptor for these proteins

◆ Antibodies :- These are the most important proteins that are involved in immune response produced by B lymphocytes.When an antigen encounters a cell then B lymphocytes produce antibody to show response against the antigen..These antibodies fit with antigen in a lock and key fashion.There are 5 major classes of antibodies which are IgG,IgA,IgM,IgD,IgE .These are immunoglobin proteins.

IgG can cross placenta and pass immunity to new born from mother

IgM first formed antibodies in response to infection

IgE are responsible for allergic reaction.

Antibody has a Y shaped structure and 4 polypeptide chains.Two heavy chains and two light chains .These chains are joined togather by disulphide bond.One chain consists of two regions that are constant and variable region.Variable region is antigen binding site

◆ Complement system:-Complement system consists of a number of small proteins that are synthesized by liver and circulate in blood as inactive precurssor.These stimulate the phagocytes to clear foreign and damaged material .Over 30 proteins and protein fragments make up the complement system including serum proteins and membrane receptors.These account for 10% of globulin fraction of blood serum.

Antigen binding site Antigen binding site Light chain Disulphide bonds Heavy chain Light chain C STRUCTURE OF ANTIBODY MOLECULE

Antigen Antibody (IgG) C1 complex C2a and C4b fragments Classical pathway C3 convertase Alternative pathway C3 hydrolysis Complement cascade C3b and C3a fragments C3b cleaves C5 into C5a and C5b Cell swells and bursts C5, C6, C7, C8 and C9 together form the cylindrical membrane attack complex