Overview of B and T Cell Preparation in Fighting Infections

B Cells Development

• Origin: B cells originate from the bone marrow.
• Unique Process:
  • Unlike other cells, each B cell daughter has a different receptor than its parent or siblings.
  • Receptors are precursors to antibodies.
  • DNA shuffling occurs during B cell maturation, creating unique receptors for identifying specific pathogens.
• Specificity: Each receptor targets a unique pathogen, rendering it highly specific but very effective.

T Cells Development

• Origin: T cells develop in the thymus, located behind the sternum.
• Receptor Formation:
  • T cells also develop unique receptors through a similar random generation process.
  • Receptors identify unique antigens presented by antigen-presenting cells.

Migration to Lymph Nodes

• Purpose of Migration:
  • Once developed, B and T cells migrate to lymph nodes (around 600 in the body) to wait for their specific pathogen.
  • Lymph nodes act as waiting areas for these immune cells.

Infection Response

• Initial Reaction:
  • Dendritic cells in tissues ingest bacteria causing infection and present antigens via MHC proteins.
  • Bacteria and antigen-presenting cells travel to lymph nodes.
• Recognition:
  • T cells require antigen-presenting cells to recognize pathogens.
  • B cells can directly bind to pathogens.
  • Only specific B and T cells with matching receptors get activated.

Clonal Selection and Activation

• Replication:
  • Activated B and T cells replicate extensively.
  • Descendant cells share the same receptor ensuring specificity for the current infection.
• Effector and Memory Cells:
  • Effector cells combat the current infection.
  • Memory cells are preserved for future infections by the same pathogen.

Clonal Selection Theory

• Definition:
  • The process of identifying and cloning specific B and T cells needed to fight an infection is termed clonal selection.
  • This theory explains the preparation of immune cells from bone marrow and thymus to lymph nodes and their response to infection.