Summary of the Specific Immune System Lecture

B Cells

• Introduction

  • B cells have membrane-bound antibodies with a variable portion unique to each B cell.
  • Different B cells respond to different antigens/pathogens.

• Activation Process

  • Requires binding of a pathogen/antigen to its antibodies.
  • Often needs stimulation by a helper T cell.
  • B cell acts as an antigen-presenting cell (APC), presenting the antigen on MHC2 complex.

• Differentiation

  • Upon activation, B cells clone themselves and differentiate into:
    • Effector Cells: Termed plasma cells, produce antibodies.
    • Memory Cells: Remain in the system for a quicker response upon re-exposure.

• Plasma Cells

  • Plasma cells are specific effector B cells that produce antibodies.
  • Common term for antibody-producing cells is plasma cells, not B cells.

T Cells

• Types of T Cells

  • Two major types based on surface proteins:
    • CD4 Positive T Cells: Often referred to as helper T cells.
    • CD8 Positive T Cells: Typically cytotoxic T cells.

• Activation and Function

  • CD4 Positive T Cells (Helper T Cells)
    • Bind to MHC2 complexes on professional APCs (like dendritic cells).
    • Upon activation, differentiate into effector and memory cells.
    • Effector helper T cells release cytokines (alarm signals) and activate B cells and assist in activating cytotoxic T cells.
  • CD8 Positive T Cells (Cytotoxic T Cells)
    • Bind to MHC1 complexes on all nucleated cells.
    • Kill infected or bad cells (e.g., virus-infected or cancerous cells).
    • Upon activation, differentiate into effector and memory cells.

Key Points

• Terminology

  • Effector B cells are commonly termed plasma cells after differentiation and are responsible for antibody production.
  • CD4 and CD8 are markers for differentiating T cell function.

• Memory Cells

  • Both B and T cells form memory cells for faster response in future encounters with the same antigen.

• Cytokines

  • Helper T cells release cytokines to boost the immune response by activating other immune cells.

This lecture introduced nuances in T cell nomenclature and clarified the roles of B cells and plasma cells in antibody production.