They functions as antibodies. The functions of immunoglobulin are agglutination, precipitation, opsonisation, neutralization etc.,

The immunity that an individual acquires after birth is known as acquired immunity. It is the body's resistance to a specific pathogen.

The immune responses may be primary or secondary.
(i) The primary immune response occurs when a pathogen comes in contact with the immune system for the first time.
(ii) The secondary immune response occurs when a person is exposed to the same antigen again. During this time, immunological memory has been established and the immune system can start producing antibodies immediately. Within hours after recognition of the antigen, a new army of plasma cells are generated. Within 2 to 3 days, the antibody concentration in the blood rises steeply to reach much higher level than primary response. This is also called as "booster response".

(i) Whenever a particulate antigen interacts with its antibody, it would result in clumping or agglutination of-the particulate antigen, which is called agglutination reaction.
(ii) The antibody involved in bringing about agglutination reaction is called agglutinin.

Based on their functions, lymphoid organs are classified into primary or central lymphoid organs and secondary or peripheral lymphoid organs.
(i) The primary lymphoid organs provide appropriate environment for lymphocytic maturation. Eg. Thymus gland.
(ii) The secondary lymphoid organs trap antigens and make it available for mature lymphocytes, which can effectively fight against these antigens. Eg. Spleen.

(i) In the 195"os,experiments by Porter and Edelman revealed the basic structure of the immunoglobulin.
(ii) An antibody molecule is Y shaped structu re that comprises of four polypeptide chains, two identical light chains (L) of molecular weight 25,000 Da (approximately 214 amino acids) and two identical heavy chains (H) of molecular weight 50,000 Da (approximately 450 amino acids).
(iii) The polypeptide chains are linked together by di-sulphide (S-S) bonds. One light chain is attached to each heavy chain and two heavy chains are attached to each other to form a Y shaped (Fig.) structure. Hence, an antibody is represented by H₂L₂.
(iv) Each chain (L and H) has two terminals. They are C - terminal (Carboxyl) and amino or N-terminal.
(v) Each chain (L and H) has two regions. They have variable (V) region at one end and a much larger constant (C) region at the other end.
(vi) Antibodies responding to different antigens have very different (V) regions but their (C) regions are the same in all antibodies.
(vii) In each arm of the monomer antibody, the (V) regions of the heavy and light chains combines to form an antigen - binding site shaped to 'fit' a specific antigenic determinant. Thus each antibody monomer has two such antigen - binding regions.
(viii) The (C) regions that forms the stem of the antibody monomer determine the antibody class and serve common functions in all antibodies.

The different types of antigen-antibody reaction are:
(i) Precipitin: The reaction between soluble antigen and antibody leads to visible precipitate formation, which is called precipitin reaction. Antibodies that bring about precipitate formation on reacting with antigens are called as precipitins.
(ii) Agglutinstion: Whenever a particulate antigen interacts with its antibody, it would result in clumping or agglutination of the particulate antigen, which is called agglutination reaction. The antibody involved in bringing about agglutination reaction is called agglutinin.
(iii) Opsonisation: Opsonisation or enhanced attachment is the process by which a pathogen is marked of ingestion and destruction by a phagocyte. Opsonisation involves the binding of an opsonin i.e., antibody, to a receptor on the pathogen's cell membrane. After opsonin binds to the membrane, phagocytesare attracted to the pathogen. So, opsonisation is a process in which pathogens are coated with a substance called an opsonin, marking the pathogen out for destruction by the immune system. This results in a much more efficient phagocytosis.
(iv) Neutralization: The neutralization reactions are the reactions or antigenantibody that involve the climinai ion of harmful effects of bacterial exotoxins or a virus by specific antibodies. These neutralizing substances i.e., antibodies are known as antitoxins. This specific antibody is produced by a host cell in response to a bacterial exotoxin or corresponding toxoid.

A vaccine is a biological preparation that provides active acquired immunity to a particular disease and resembles a diseasecausing microorganism and is often made from weakened or atlenuated or killed forms of the microbes, their toxins, or one of its surface proteins. The vaccines are classified as first, second and third generation vaccines.

Both A and R are false

iv only

Reason: It is not linked to immune system whereas the others are Iinked to Irnmune system.

diapedesis
Reason: It is not a type of antigen-antibody reaction whereas others are types of antigenantibody reactions.

neoplasm

haematopoiesis

immunity