Antibodies

B Lymphocytes and Antibodies

• B lymphocytes become plasma cells, producing antibodies based on the body's needs.
• Five types of antibodies: IgM, IgA, IgD, IgG, IgE.

Antibody Functions

• IgM (Immunoglobulin M): First antibody released; activates complement proteins.
• IgA (Immunoglobulin A): Found in body fluids (mucus, tears, sweat); prevents pathogen entry.
• IgD (Immunoglobulin D): Attached to B lymphocytes; acts as a cell receptor.
• IgG (Immunoglobulin G): Major antibody (75-85%); crosses placenta, provides passive immunity; active in late primary and secondary immune responses.
• IgE (Immunoglobulin E): Associated with allergies and parasitic infections.

Memory Cells and Immune Response

• Plasma cells also create memory cells, which provide immunological memory for swift response to re-exposure to antigens.
• Secondary immune response activates quickly (hours) with peak antibody levels in 2-3 days.

Cellular Immunity

• Involves T lymphocytes; defends against intracellular antigens (viruses, bacteria, cancerous cells, transplanted tissue).

Immunity Definition

• Immunity: Resistance to disease, including response to infections or toxins.

Types of Immunity

Active Immunity

• Immunological memory; two types:
  • Naturally acquired: From actual infections.
  • Artificially acquired: Through vaccination (dead/weakened pathogens).

Passive Immunity

• Immediate but short-term protection; no immunological memory; two types:
  • Naturally acquired: Antibodies from breast milk to baby.
  • Artificially acquired: Immunoglobulin therapy (intravenous); transient effect lasting 3-4 weeks.