Immunity

Keywords: Antigen| antibody| autografts | active |passive immunity| humoral |cell mediated immunity|

|Table of contents

1.	Introduction
2.	Classification
3.	Antigen
4.	Types
5.	Grafts
6.	Antibody
6.	Functions

Introduction

Immunity is derived from the Latin ‘immunitas,’ meaning exemption from public services tax payments, etc. Ilya Mechnikov, in 1882, described a detailed study of immunity. In human physiology, immunity is defined as the capability to resist the entry of microorganisms and destroy the harmful material in the body. This system is also known as a defense system.

Immunity is a complex system involving multiple systems and different types of cells and chemicals. The immune system recognizes and tolerates its tissues -whatever belongs to the self and recognizes, rejects, and destroys foreign- non-self cells.

The science of immunology studies human resistance to infection and includes many autoimmune disorders. Immunity is a pervasive topic. This article will teach critical points to have a clear concept of immunity.

Classification

1. Non-specific or First line of defense protects the body against invading organisms by providing a physical barrier. For example, skin, epithelial lining, and secretions like tears and saliva provide physical barriers.
2. The specific or second line of defense starts working when the first line of defense fails, and the organism invades the human body, performed by the ‘immune system.’

Classification of immunity:

Naturally acquired =natural or innate immunity: protects against infectious microorganisms through

1. Mechanical barrier- intact skin, mucous coat, cough, vomiting.
2. Physiological factors-Hormones, body temperature, the Oxygen concentration in tissues.
3. Body secretions- tears, saliva, vaginal secretion, HCl secretion in the stomach, and urine are examples of natural immunity..
4. Phagocytosis- Phagocytosis by neutrophils, basophils, eosinophils, and monocytes.

Naturally acquired immunity

Active -immunity develops after infection of the disease, for example, after a smallpox infection. In some cases, immunity is lifelong.

Passive – Antibodies passively come to the fetus from the mother and provide immunity.

Artificial immunity is also of two types

1. Active-body makes antibodies after exposure to

vaccines.

2. Passive -Prepared antibodies are given to provide immunity.

Types of immunity:

Active immunity is produced by the body itself and is long-lasting. This immunity may be:

1. Due to infection 2. Due to prophylactic exposure to a pathogenic organism or its toxins 3. Active immunization, for example, active immunization against many diseases-polio, tetanus. And recently against Coronavirus.

Passive immunity is due to transferring immunization products -serum, antibody, or lymphoid cells -to a non-immune individual. The immunization outcomes -serum, antibody, or lymphoid cells are formed in another individual -the human source. Products of immunization -serum, antibody, or lymphoid cells may be obtained from animal sources.

Another classification is based on the mode of action:

1. Humoral immunity by the formation of antibodies.

2. Cell-mediated immunity by specifically primed lymphocytes.

Types of immune response

The primary response occurs after several days of first exposure to a new antigen. It is for a short period and is small in amplitude.

The secondary response occurs following a second exposure to the same antigen. Again, the answer is quick and high in amplitude that persists for a long time. Therefore booster doses are given.

Antigen

The antigen is a biologically active substance that is immunogenic. The term immunogenic means capable of evoking an immune response. They are usually composed of proteins, polysaccharides, and mucopolysaccharides.

An antigen must have two properties:

1. Immunogenicity and 2. Antigenicity

Immunogenic substances are always antigenic, but antigens are not always immunogenic.

Antigenicity is the specific reactivity of an antigen. It triggers the production of a particular antibody or cell and reacts specifically with that.

All types of microorganism-bacteria, foreign proteins that enter the body without being broken down by the gastrointestinal tract proteolytic enzymes, are antigens.

Antigens must be foreign or alien (of a different nature -not one’s own) to the host to cause immunogenicity. Types :

1. Autologous antigens -an autograft-skin graft from thigh to back within the same individual.
2. Syngenenic antigens -in identical twins.For example, syngeneic graft or isograft-a graft between identical twins.
3. Allogenic antigens=homologus antigens within the same species but different individuals. For example, allograft or homograft from mother to daughter.
4. Xenogenic=heterologous antigens are present across species—for example, xenograft or heterograft- pig liver transplant to human.

Antibody

Antibody formation is the essential physiological response to antigens. Antibody formation is peculiar to the antigen and combines specifically with the antigens that trigger it.

Chemically antibodies are immunoglobulins and circulate in the blood. All lymphoid tissues of the body form antibody except the Thymus. B-lymphocytes are transformed into plasma cells that will synthesize immunoglobulins.

Functions

Protection from infection.

It helps to identify proper graft donors.

Sometimes it is harmful and produces autoimmune diseases.

Is there any food that will boost my immunity?

No food will increase your immunity except a well-balanced diet, exercise, a healthy lifestyle, and a positive attitude.

A well-balanced diet consists of carbohydrates, proteins, fat, minerals, vitamins, and water in adequate amounts.

Proper immunization is essential as directed by local authority and medical experts.

Internal Link: https://blog.totalphysiology.com/2021/01/white-blood-cell leucocytes.html

https://blog.totalphysiology.com/2021/05/digestion-and-absorption-of-protein.html

External Link: https://en.m.wikipedia.org/wiki/immunity_(medical)