Immunity and its types /immunisation

INNATE IMMUNITY:

- it is present from birth and is inherited from the parents.

(1) it is non-specific.

(2) it consists of following types of barriers

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(a) PHYSICAL BARRIERS:

- prevent entry of microorganisms in the body, eg,.

Skin, mucus coating of the epithelium lining the

respiratory, gastrointestinal and urogenital tracts.

Mucus traps the microbes entering our body.

(b) PHYSIOLOGICAL BARRIERS:

- prevent microbial growth in the body, eg. Acid in

the stomach, lysozyme in saliva of mouth and the tears from eyes.

- phagocytose and destroy microbes. For example,

some leucocytes (WBCs) like polymorphonuclear

leukocytes (PMNL), monocytes and natural killer

cells (type of lymphocytes) in the blood as well as macrophages in tissues.

(d) CYTOKINE BARRIERS :

- are virus - infected cells, which secrete proteins

called interferons They protect non-infected cells from further viral infection.

ACQUIRED IMMUNITY:

- It is not present from birth and develops during an individual lifetime.

(1) it is pathogen specific, can differentiate

between self and non-self cells and characterised

by memory.

(2) when it encounters a pathogen for the first

time, it produces a response called PRIMARY

RESPONSE, which is low intensity and takes time.

(3) further encounter with same pathogen

produces highly intensified SECONDARY or

ANAMNESTIC RESPONSE due ti the memeory of first encounter.

(4) cells of immune response immune response are produced by two types of lymphocytes

(a) B-lymphocytes or B-cells produce an army of

proteins (in response to pathogens) called antibodies in blood.

B-lymphocytes are formed in bone marrow and

their maturation also takes place in bone marrow.

(b) T-lymphocytes or T-cells help B-cells to

produce antibodies bit they themselves do not secrete these antibodies.

T-lymphocytes are formed in bone marrow but their maturation takes place in thymus gland.

These topic is very important for Neet students.

-on the basis of type of immune response, acquired immunity is of the following two types

(a) HUMORAL IMMUNE RESPONSE OR ANTIBODY-MEDIATED IMMUNITY(AMI)

- it is mediated by antibodies present in the body

fluid (humours) like blood and lymph,. When a

pathogen enters in body, the B-cells encounter

them and produce to different types of antibodies which are released in the blood.

(b) CELL-MEDIATED IMMUNE RESPONSE OR CELL-MEDIATED IMMUNITY (CMI)

-it is mediated by T-lymphocytes, here antibodies

are not produced by T-lymphocytes instead they

recognise the non-self cells. These T-lymphocytes

then act by their phagocytic ability to kill the

pathogen. The graft rejection during organ

transplantation occurs, because of the ability of

the T-lymphocytes to differentiate between self

and non-self, due to the cell-mediqted immunity.

That is why blood group and tissue matching are

essential before organ transplantation.