Immunity is the body's ability to resist harmful microorganisms and other pathogens. It can be categorized into several types, broadly divided into innate (or natural) immunity and adaptive (or acquired) immunity. Here's a detailed breakdown of each type

Innate Immunity

Innate immunity is the first line of defense against pathogens and is present from birth. It includes:

1. Physical Barriers: arrier to prevent pathogens from entering the body.

-Mucous Membranes: Found in the respiratory, gastrointestinal, and genitourinary tracts, these membranes secrete mucus to trap pathogens.

2. Chemical Barriers:

- Stomach Acid: Destroys pathogens that are ingested.

- Enzymes in Saliva and Tears: Contain lysozymes that break down bacterial cell walls.

- Antimicrobial Proteins: Such as defensins and interferons.

3. Cellular Defenses:

- Phagocytes: Cells like neutrophils and macrophages that engulf and destroy pathogens.

- Natural Killer (NK) Cells: Target and destroy infected or cancerous cells.

- Dendritic Cells: Present antigens to adaptive immune cells, linking innate and adaptive immunity.

4. Inflammatory Response:

- A rapid response to infection or injury, involving increased blood flow, heat, swelling, and recruitment of immune cells to the site of infection.

Adaptive Immunity

Adaptive immunity is more specific and has memory, meaning it can provide long-lasting protection. It develops after exposure to antigens. Adaptive immunity is divided into:

1. Humoral Immunity:

- B Cells: Produce antibodies that bind to specific antigens.

- Antibodies: Neutralize pathogens, mark them for destruction, or prevent them from entering cells.

2. Cell-Mediated Immunity:

- T Cells: Differentiate into various types (e.g., helper T cells, cytotoxic T cells) to target and destroy infected cells.

- Helper T Cells: Assist other immune cells by releasing cytokines and promoting immune responses.

- Cytotoxic T Cells: Directly kill infected or cancerous cells.

Types of Adaptive Immunity

Adaptive immunity can further be categorized based on how it is acquired:

1. Active Immunity:

- Natural Active Immunity: Results from an infection; the body produces its own antibodies and memory cells.

- Artificial Active Immunity: Acquired through vaccination; exposure to a weakened or inactive form of the pathogen stimulates an immune response.

2. Passive Immunity:

- Natural Passive Immunity: Transfer of antibodies from mother to baby through the placenta or breast milk.

- Artificial Passive Immunity: Involves the injection of antibodies from another person or animal (e.g., antiserum or antitoxin).

Summary

• Innate Immunity: First line of defense, non-specific, present from birth. Includes physical barriers, chemical barriers, cellular defenses, and inflammatory response.

• Adaptive Immunity: Specific, has memory, and develops after exposure to antigens. Includes humoral immunity (B cells and antibodies) and cell-mediated immunity (T cells).

• Active Immunity: Body produces its own immune response (natural through infection or artificial through vaccination).

• Passive Immunity: Body receives antibodies from another source (natural through maternal transfer or artificial through antibody injections).