Immune System

• What do you already know about the immune system?

Name Description Antibody Complexes

IgA Found in mucosal areas, such as the gut, respiratory tract and urogenital tract, and prevents colonization by pathogens. Also found in saliva, tears, and breast milk.

IgD Functions mainly as an antigen receptor on B cells that have not been exposed to antigens.Its function is less defined than other isotypes.

IgE Binds to allergens and triggers histamine release from mast cells and basophils, and is involved in allergy. Also protects against parasitic worms.

IgG In its four forms, provides the majority of antibody-based immunity against invading pathogens. The only antibody capable of crossing the placenta to give passive immunity to fetus.

IgM 1 Expressed on the surface of B cells and in a secreted form with very high avidity. Eliminates pathogens in the early stages of B cell mediated (humoral) immunity before there is sufficient IgG.

• IgA antibodies are found in areas of the body such the nose, breathing passages, digestive tract, ears, eyes, and vagina. IgA antibodies protect body surfaces that are exposed to outside foreign substances. This type of antibody is also found in saliva and tears. About 10% to 15% of the antibodies present in the body are IgA antibodies. A small number of people do not make IgA antibodies.

• IgG antibodies are found in all body fluids. They are the smallest but most common antibody (75% to 80%) of all the antibodies in the body. IgG antibodies are very important in fighting bacterial and viral infections. IgG antibodies are the only type of antibody that can cross the placenta in a pregnant woman to help protect her baby (fetus).

• IgM antibodies are the largest antibody. They are found in blood and lymph fluid and are the first type of antibody made in response to an infection. They also cause other immune system cells to destroy foreign substances. IgM antibodies are about 5% to 10% of all the antibodies in the body.

• IgE antibodies are found in the lungs, skin, and mucous membranes. They cause the body to react against foreign substances such as pollen, fungus spores, and animal dander. They may occur in allergic reactions to milk, some medicines, and some poisons. IgE antibody levels are often high in people with allergies.

• IgD antibodies are found in small amounts in the tissues that line the belly or chest. How they work is not clear.

• Lymphocytes come in three flavors, B-cells, T-cells, and Natural Killer (NK) cells.

• B-cells can become plasma cells and produce antibodies. • T-cells exist in 2 forms, helper T-cells and killer T-cells.

– Helper T-cells are a bit like antibodies and help tag bacteria for destruction.

– Killer T-cells and NK cells do exactly what it sounds like they do -- they kill bacteria.

– Monocytes are big and slow Pacman-like cells that eat other cells whole. – It can take 3-5 days for these bad boys to arrive on the scene, and so

the immune system has neutrophils, which are smaller and stealthier. Basophils are basically wimps. Eosinophils fight crime in the form of parasitic infections

Reproduction

Cortical Reaction Prevents ???

• Once fertilization has occurred, the primordial cell, called the zygote, migrates to the lining of the uterus. While doing so, this cell undergoes successive divisions, soon forming an embryo with 2 cells, then 4, then 8, and so on.

• The first three-dimensional structure that emerges from these cell divisions is a sphere of cells. The term morula is used to designate the ensuing stages of embryonic development (16, 32,and 64 cells). The morula is thus the product of the first cell cleavages, which result in practically no growth, because the daughter cells become smaller and smaller.

• The morula is like a solid ball. But after the 64-cell stage, this ball develops an inner cavity, called the blastocoele, thus becoming a blastula.

The blastula becomes the gastrula when the invaginated cells have formed the ectoderm and the endoderm.