Definition
Immunity refers to the body's ability to resist and fight off infections and diseases.
It is the natural defense mechanism of the body that helps to keep us healthy and protects us from harmful invaders like viruses, bacteria, and parasites.
Types of Immunity
There are two main types of immunity: innate immunity and adaptive immunity.
1) Innate Immunity
This is the first line of defense against pathogens and is present from birth.
It includes:
Physical barriers such as the skin and mucous membranes.
Immune cells like neutrophils, natural killer cells, and macrophages.
Innate immunity provides immediate protection against infections but is non-specific and does not provide long-term immunity.
2) Adaptive Immunity
This type of immunity develops over time as the body is exposed to different pathogens.
It is mediated by specialized immune cells called T cells and B cells, which can recognize and respond to specific pathogens.
Adaptive immunity takes time to develop but provides long-lasting protection against specific pathogens through the production of antibodies and memory cells.
There are two types of adaptive immunity:
A) Humoral Immunity
Involves the production of antibodies by B cells.
These antibodies recognize and neutralize pathogens in the bloodstream.
B) Cell-Mediated Immunity
Involves the activation of T cells.
T cells can directly kill infected cells and help regulate immune responses.
