Lines of Defense in Immune System

Deeksha Sriram & Sajani Raja

Innate Immunity

Skin and Body Secretions

-Skin is the physical barrier that microorganisms have to pass

-Mucus which is supposed to prevent areas of the body from drying out

-Sweat, tears, and saliva contain lysozyme which can destroy the cell wall of some bacteria

-Gastric juice in the stomach destroys most bacteria

Inflammation of Body Tissues

-4 symptoms- redness, swelling, pain, and heat

-It occurs when pathogens damage body tissues

-Tissue cells called "mast" cells and white blood cells called "basophils" release histamine

-Histamine causes blood vessels to dilate, making the permeable to tissue fluid

-This tissue fluid helps destroy toxic agents

-Response to injury


Phagocytosis of Pathogens

-Phagocytes are white blood cells that destroy pathogens by engulfing them

-They include- monocytes (which develop into macrophages), neutrophylles, and eosinophils.

-Macrophages are in body tissues, the others are in the blood

-Macrophages are the white blood cells that provide the first defense against pathogens

-Lysosomal enzymes inside macrophages digest the particles they engulf.

-Neutrophylles only help when macrophages fail

-The third method of defense are monocytes (which are immature macrophages). They squeeze through blood vessels to get to the infected area. When they reach the site of infection, they become macrophages.

-Puss forms until the infection clears

Protective Proteins

-Protective proteins are used to help fight viruses

-Interferons protect cells from viruses. They are host cell specific.

-It is produced by a body cell that has been infected by the virus

-Diffuses to uninfected neighboring cells to prevent the virus from multiplying

Acquired Immunity

The Lymphatic System

-Defense against the pathogen by gradually building up resistance

-Produces antibodies to defend against diseases

-Keeps body fluids at a constant level

-Lymph carries pathogens and filters them through lymphnode

-A lymphasite is a type of white blood cell that defends the body against foreign substances

-Tonsils are clusters of lymph tissues

Anitbody Immunity

-T cells become involved

-T cells are lymphacites produced in bone marrow that play roles in immunity

-Helper T cells interact with B cells

-B cells are lymphacites that produce antibodies when activated by T cells

-B cells become plasma cells and release antibodies into the bloodstream and tissue

-Memory B cells remain in the body in case the same pathogen invades that body later


Cellular Immunity

-Involves sinotoxic T cells

-They produce identical clones of themselves

-They travel to the infection site and release enzymes directly into the pathogens causing the pathogens to lyse and die


Passive Immunity

-Develops naturally when antibodies are transferred from mother to child through classenta

-Develops artificially when antibodies are injected


Active Immunity

-Obtained naturally when one is exposed to antigens

-Can be induced artificially by vaccines