Immunology & Blood Banking

 Introduction

 Immunity: Resistance or defense against harmful agents/substances causing disease.

 Immune System: Cells and molecules defending the body against environmental pathogens.

 Antigen: Substance stimulating an immune response.

 Antibodies: Proteins reacting to antigens.

 

Self vs NonSelf

 Self: Cells, fluids, molecules, and structures from the host.

 NonSelf: External substances, living organisms (parasites, fungi), nonliving toxins, or host derived genetic rearrangements.

 

Types of Immunity

 Innate or Natural Immunity: Primary, nonspecific defense present at birth, not altered by repeated exposure.

 Acquired or Adaptive Immunity: Specific, acquired through contact with foreign substances, has memory improving response with each encounter.

 

Innate Immunity

 First Line of Defense: Physical barriers like intact skin, mucous membranes.

 Second Line of Defense: Cellular components like phagocytic cells, macrophages, NK cells, and humoral factors like complement pathways, cytokines.

 

Acquired Immunity

 Naturally Acquired Immunity:

   Active: Body produces antibodies after disease or infection.

   Passive: Maternal antibodies passed to fetus or through breast milk.

 Artificially Acquired Immunity:

   Active: Vaccination with dead or weakened pathogens.

   Passive: Injection of readymade antibodies.

 

Components of Acquired Immunity

 Humoral Immunity: Mediated by antibodies produced by B lymphocytes, targets extracellular microbes.

 Cell Mediated Immunity: Mediated by T cells, involves cytokines, combats intracellular pathogens.

 

Cytokines

 Proteins involved in cell signaling, produced by various cells like T cells, macrophages.

 Functions include induction of proinflammatory proteins, proliferation of immune cells, regulation of immune responses.

 

Immune System Cells & Organs

 Lymphocytes:

   T Lymphocytes: Mature in thymus, produce cytokines, destroy infected cells.

   B Lymphocytes: Mature in bone marrow, become plasma cells secreting antibodies.

   Natural Killer Cells: Combat viral infections.

 Dendritic Cells: Process and present antigens.

 Macrophages: Process antigens, contribute to immune response.

 

B Lymphocytes (B Cells)

 Produce antibodies (plasma cells), important in recognizing and neutralizing pathogens.

 Activated B cells differentiate into plasma cells and memory B cells.

 

T Cells

 Recognize internalized antigens, involved in fungal/viral infections, intracellular parasites, tissue grafts, and tumors.

 MHC Molecules: Required for T cell recognition, MHC Class I on most nucleated cells, MHC Class II on antigen presenting cells.

 

Blood Banking Importance

 Antibody testing ensures blood supply safety, screens for infectious diseases, identifies transfusion reaction risks.

 Compatibility testing critical for safe transfusions.