October 7th 2015 T and B cells There are 3 questions The first 2 should require only a few sentences The 3rd question may be a little longer Please write in complete sentences 1 What is the difference between a stem cell and a differentiated cell Stem cells are undifferentiated cells which when they divide give one differentiated daughter cell and another stem cell Stem cells are primarily found in the bone marrow Differentiated cells are cells that are more specialized in function than the original cell it divided from These differentiated cells also called precursors will go on to produce all the cells in the body 2 Discuss the levels of IgM and IgG in a fetus a newborn and an adult include the antibody level and who made the antibody Based on the graph given in Dr Cohen s powerpoint and what she said in class IgM is made by the fetus in its third month of development in the womb At birth the level is of that in an adult Around 10 12 months the baby s level of IgM is equal to an adults IgM is completely made by the fetus Again based on the graph given in Dr Cohen s powerpoint and what was discussed in class IgG in the fetus is completely maternally derived IgG is the only Ig that can cross the placenta and is what is used for the fetus At birth the level of IgG is 100 maternal and 100 of the level in an adult Around 3 months old the baby will then begin to create its own IgG because the maternal IgG levels drop to about 30 of what an adults level of IgG would be 3 What is the process that B cells go through from a pre B cell through antibody production The process that B cell development is a result of alternative splicing First a pro B cell splices its mu chain and divides This is done by splicing the VDJ region to create a different type of Ig heavy chain After this the cell rearranges its light chain to create a cytoplasmic IgM also known as cIgM and become a pre B cell This is done by alternatively splicing the VJ regions in order to create a specific light chain This is now a pre B cell as Dr Cohen s Ontogeny notes dictate that a pre B cell is a cell with cytoplasmic IgM but no surface IgM After this a surface IgM creates an immature B cell Eventually a B cell becomes mature when surface IgM and surface IgD are bound to the B cells outer membrane When a mature B cell with its IgM and IgD receptors are exposed to the right antigen they are brought into the cell and are partially digested If the correct conditions are met the cell will go onto differentiate into an antibody secretor also known as a plasma cell Citations Cohen Z Fall 2015 Ontogeny of the Immune System In Immunology