immune system and lymph

What does the lymphatic system do?

• Monitors both body surface and interior

• Reacts to potential harmful substances

• Cells, tissues, organs

  • Lymphocytes!!

• Anything in lymphatic system will end up in vascular system

Lymph vessels ←→ Lymph nodes

Lymph vessels connect lymph nodes to form a chain filtering lymph as it flows toward the two final vessels and drain into the brachiocephalic veins

Antigen

bad guys (molecules) recognized by immune cells to induce a specific immune response

Some can activate the complement system: helping the antibodies do their work

Antibody

Protein that marks invaders for destruction by other immune cells

Interact with antigens at an antigen-binding site and can bind to them for other cells to come and attack

B Cells (Lymphocyte)

Leaves the bone marrow with knowledge of multiple antigens it can recognize to attack

Produce plasma cells

T Cells

Leave thymus with T-cell receptors (TCRs)

• Helper cells

• Cytotoxic T cells

• Regulatory T cells

Natural Killer (NK) Cells

Attack virus infected cells, transplanted cells, and cancer cells

Antigen Presenting Cells (APCs)

Macrophages, dendritic cells, and B-lymphocytes

They capture antigens and shares the antigen with helper T-cells

Innate reponse

Fast and non-specific

• Neutrophils

• Macrophages

• Mast cells

• NK cells

Adaptive response

Requires initial recognition by B and T cells thus slower and more specific

Produces memory cells to respond quickly to future exposure of that antigen

Humoral (Adaptive response)

B-lymphocytes will produce plasma cells that produce antibodies

Cellular (Adaptive response)

Helper T-lymphocytes get activated when come into contact with an antigen —> release cytokines —> attract and recruit other cells in to fight

Naive T and B cells

When T and B cells are fresh out of bone marrow and migrate to lymphoid tissues but are not yet challenged by a specific foreign antigen

T cells will proceed to thymus for selection

Major Histocompatibility Complex

• MHC I proteins on all nucleated cells

  • Activated T-cells will kill antigen on APCs but MHC I tells them not to kill the APC itself

• MHC II on B cells and macrophages

T-cell selection

Occurs in thymus (hence “T”)

1. Expression of CD marker and T-cell receptors (TCRs)

2. CD4 (Helper T cells) bind to MHC II

3. CD8 (cytotoxic T cells) bind to MHC I

4. Remove T-cells that do not react to antigens or react against self antigens

Only 2% of cells survive this selection process

Components of lymph tissue

• Loose connective tissue with lymphocytes and other cells and reticular fibers

• Lymphoid nodules can be free or enclosed

  • Nodules mainly contain B lymphocytes

Thymus Gland

Site of T-cell maturation and selection

Consists of outer cortex and inner medulla

• cortex is rich in small lymphocytes relative to medulla

Tonsil tissues

Bad things from outside environment can enter in through nose and mouth so a bunch of tonsil tissues is there to prevent that

• Palatine tonsils

• Lingual tonsils

• Pharyngeal tonsil

• other MALT

Lymph node

Lymph nodes have high endothelial venules (HEVs) to promote rapid transit and recirculation of lymphocytes

• HEVs are specialized postcapillary venules