Humoral Response in Immunity

Overview

Focus on B-cells and antibodies
Humoral response is part of the specific immune response
B lymphocytes (B-cells) are white blood cells involved in responding to particular antigens
All lymphocytes, including B-cells, are made and mature in the bone marrow
Term "humoral" comes from "humor," an old term for body fluids, because antibodies are soluble and circulate in body fluids

Approx. 10 million different lymphocytes, each capable of creating different antibodies
Antibodies on B-cells are complementary to different antigens
When a B-cell encounters its complementary antigen, it takes it in by endocytosis and presents it on its surface
Interaction with helper T-cells activates the B-cell for clonal expansion and differentiation
Clonal selection results in:
- Plasma cells: Produce antibodies
- Memory B cells: Remain in the body for decades, can rapidly divide into plasma cells when encountering the same antigen again

Primary response: First exposure to an antigen, slower and less antibody production
Secondary response: Faster and more robust due to memory B cells, prevents symptoms of infection
This graphically represented by increased antibody concentration over time during second exposure

Proteins with quaternary structure
Comprised of four polypeptide chains:
- Two long (heavy) chains
- Two short (light) chains
Variable region: Complementary to specific antigens
Constant region: Same across different antibodies

B-cells respond to foreign antigens through clonal selection
Produce monoclonal antibodies
Plasma cells release antibodies, memory cells facilitate rapid response upon re-exposure
Antibodies bind to antigens, leading to pathogen destruction via agglutination