Lymphatic System Structures and Lymphocytes

Lymphatic System Structures

Lymphocytes (Lymphoid Cells)

  • Leukocytes (WBCs) from bone marrow.

    • lymph\/o = lymph, −cytes-cytes = cells

  • Defend against antigens (foreign substances like viruses, bacteria, toxins).

    • Antigen example: viruses, bacteria, toxins, transplanted tissues

  • Types: Natural Killer (NK) cells, B cells, T cells.

  • Mature and differentiate in lymphoid tissues - become specialized antibodies.

Natural Killer (NK) Cells

  • Kill cancer cells and virus-infected cells.

B Cells (B Lymphocytes)

  • Produce antibodies.

  • Each B cell makes a specific antibody for a specific antigen.

  • Effective against viruses and bacteria in blood.

  • B cell + antigen = plasma cell (secretes many antibodies).

T Cells (T Lymphocytes)

  • Mature in thymus (hence "T").

  • Key in cell-mediated immunity.

Cytokines

  • Proteins (interferons, interleukins) from T cells.

  • Intracellular signals for immune response.

Interferons (IFNs)

  • Made when antigens (viruses, tumor cells) are present.

  • Activate immune system.

  • Fight viruses by slowing/stopping multiplication.

  • Signal other cells to increase defenses.

Interleukins

  • Direct B and T cells to divide and multiply.