immunology, how immune system works and protect from harmful diseases

What is immunology?

immunology:- Prior to birth, the human fetus lives in a practically sterile environment of the uterus. After birth, we are all exposed to a great variety of threats to our survival, throughout the life span. Preservation of the human race depends upon its ability to recognize, fight and eliminate/neutralize these potentially harmful challenges to its existence.

Immunology is the study of immunity, a physiological process by which the body protects itself from injurious agents. Most of these agents are infectious

organisms i.e., bacteria, viruses, protozoa, fungi, etc. The main components of the immune system are the complement system, cytokines, antibodies, phagocytes, lymphocytes, and antigen-presenting cells. This system can recognize all potential threats because it can differentiate between self and non-self, through antibodies (SLG) present on the surface of B-lymphocytes and T-cell receptors (TCR) on the surface of T lymphocytes.

The immune system acts in three phases

The first phase is recognition‘ It is accomplished with the help of B-lymphocyte receptors (surface immunoglobulins) and T-lymphocyte surface receptors (TCR). The second phase is that of activation‘ in which metabolic processes are activated inside the cells. The third phase is the effector‘ phase in which the activated cells produce chemicals (cytokines) to activate other cells, some differentiate into plasma cells to produce antibodies and others produce surface receptors and substances which help in cytotoxic activity. Memory cells are also generated in this phase.

There are two categories of immune mechanisms Non-specific or innate immunity and Specific or acquired immunity

NON-SPECIFIC (INNATE) IMMUNITY

The non-specific immune mechanisms are also called innate as they act against all potential injurious agents in the same manner, even after repeated exposures.

ACQUIRED IMMUNITY

Acquired/specific immunity is of two types: Active, which is generated when an individual is exposed to an antigen, and Passive, which is introduced in the body in the form of preformed antibodies or cells by injection or infusion (also called adoptive transfer). In the passive type, the components of the immune response, e.g. antibodies in serum are collected from a donor and transferred to a patient who requires an immediate immune response (such as anti-snake venom injected in a snake-bite victim). The individual becomes immune for a short period of time without being exposed to the antigen. The following properties are unique for the acquired (specific) immune system (not found in the non-specific/innate immune system)