Aim: How does our body defend us from pathogens?

Pathogens Any disease-producing agent especially a virus, bacterium, fungus, or parasite.nydiseaseproducing agentespeciallyavirus bacterium

1 st Line of Defense Skin Mucus There are often enzymes in these substances that are able to destroy pathogens (tears & sweat). Others like the stomach provide acidic environments that are inhospitable to most pathogens. Hair and mucus serve to trap potential disease causing pathogens. Tears in eyes Acid in stomach

2 nd Line of Defense The Immune System

Cellular Components: White Blood cells Large cells with a nucleus. Less numerous than RBC’s. Defenders of the body. Types: –Phagocytes: engulf and destroy bacteria (Macrophages) –Lymphocytes: produce antibodies (B-Cells)

Phagocytes Granulocytes – surround/destroy bacteria – 1 st in infection Macrophages – ‘eat’bacteria & older cells, alert rest of immune system – start as monocytes. Dendritic – eat intruders Eosinophils – kill parasites Basophils – allergic reactions – histamine & heparin

T & B Cells – WBC that migrate to lymphatic system (lymph, spleen, thymus) Helper T cells – activate B and killer T cells. Receptors on Helper T cells recognize antigen on macrophage or dendritic cell that have brought pathogen to lymph. Activated T cells divide and produce proteins that activate B and T cells Killer T – attack viral cells B cells - Y shaped antibodies. Memory Cells (B & T cells) Lymphocyte

Immune System Made of proteins, cells, and tissues that identify and defend the body against foreign chemicals and organisms

How does our immune system identify foreign cells? Protein on the cell membrane This “ID tag” identifies the invader as not belonging to the body (non-self). This ID tag is called an antigen. All cells have these recognition proteins!! Antigen Recognition proteins (Antigens) on our own cells (self) are not targeted by our own immune system.

Phagocytes – Engulf the Pathogens Phagocytes: White blood Cells that Eat a pathogen

Lymphocytes – Produce antibodies They can make antibodies, which are their weapons against the foreign antigens. Antibodies & Antigens are both proteins!!

Antibodies They are “Y” shaped proteins, made by __________ They are weapons that fight against pathogens Pathogen Antigens Antibodies B-Cells

How are antigens and antibodies similar to enzymes? Antibodies are made specifically to match the shape of the antigen. 1 antigen = 1 antibody What does this remind you of?

How do antibodies destroy pathogens? When the antibody attaches to the antigen, it breaks open its cell membrane. Or, the antibody attaches to the antigen, and a phagocyte will know to engulf it.

Our Immune System has a good memory! The first response is relatively slow and weak because time is needed for enough WBCs to form and defeat the pathogen. The second response to the same pathogen triggers a quicker and stronger response. ** After the first response, the immune system “remembers” specific pathogens by leaving behind WBCs that protect the body for years (memory cells).