Coupon Accepted Successfully!



Resistance of a host to pathogens and their toxic products.

Innate Immunity Acquired Immunity
1. Non specific
1. Natural
b. Artificial
2. Specific 2. Passive
a. Natural
b. Artificial

Innate Immunity
  1. Genetic/ Constitutional make up
  2. Prior contact not essential
  3. Species immunity
  4. Racial immunity
  5. Individual immunity
  6. Age, Hormonal influences, Sex, Nutritional factors

1.  Mechanisms Of Innate Immunity

  1. Humoral Defence Mechanisms
  2. Lysozyme, basic polypeptides, complement, interferons, acute phase reactants
  3. Cellular Defense Mechanisms
  4. Phagocytes (Neutrophils, eosiophils, basophils, monocytes/ macrophages)
2.  NK cells
  1. Fever
  2. Inflammation

B.  Acquired Immunity

  1. Resistance that an individual acquires during his life-time
  2. Antigen specific
  3. Humoral: Antibody (produced by differentiated B lymphocytes: Plasma cells)
  4. Cell mediated: T lymphocytes (CD4 and CD8)
  5. Active/ Passive immunity
Active immunity Passive immunity
Produced actively, AG stimulated Received passively
Infection/ Contact with Ag Administration of Antibody
Long lasting Transient
Lag period Effective immediately
Negative phase No negative phase
Immunological memory + No immunological memory
Not applicable in the immunodeficient Applicable in immunodeficient
Secondary response  
More effective Less effective  
Not applicable in immunodeficient Applicable in immunodeficient

1.  Active immunity:


  1. Clinical infection  
  2. Subclinical infection   
  3. Artificial    
    1. Vaccination   
    2. Live  
    3. Killed

2.  Passive immunity:

  1. Natural- Placenta, Breast milk
  2. Artificial- Immune cells, Immune serum
  3. Adoptive immunity: Injection of immunologically competent lymphocytes
  4. Local immunity: Site of invasion/ Multiplication of Pathogen; IgA antibodies
  5. Herd immunity: Overall level of immunity in a community

3.  Lymphoid System

  1. Cells involved in the immune response into tissues and organs which are collectively referred as lymphoid system
  2. Lymphoid tissue is divided into Primary & Secondary
  3. Primary (central)
    i.        Sites of lymphoid development
    ii.        T cells: Thymus
    iii.        B cells: Bone marrow
  4. Secondary (peripheral)
    1. Provide environment where lymphocytes can interact with antigens
    2. Spleen, lymph nodes, mucosa associated lymphoid tissue
    3. Spleen: T cells area (around central arteriole in periarteriolar sheath); B cell area: (primary & secondary follicles in the periarteriolar sheath)
    4. Lymph nodes: T cell area (paracortex), B cell area (cortex) 

Test Your Skills Now!
Take a Quiz now
Reviewer Name