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300-09%20Imm1%20DRAFT - Our three lines of defense BISC300L...

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IMMUNOGLOBULINS 4/15/09 1 1 BISC300L Wed., Apr. 15, 2009 Immunology 1 Immunoglobulins Chap. 27 n DRAFT VERSION print time 4/14/09 4:10 PM Why is immunology so complicated? Because if it weren ! t complicated, we ! d all be dead. We ! ll start with slides on complement from the end of the previous ppt file. Pic from Stryer IMMUNOGLOBULINS 4/15/09 2 2 Our three lines of defense Barrier defenses Innate immunity is immediate and generalized . It involves recognition of common microbial surface molecules. Prior exposure to the microbe is not necessary. Adaptive immunity is slower and specific . It involves recognition of a particular microbe. ! 1. ! 2. 3. ! It has been known for thousands of years that people get certain diseases only once: smallpox, measles, German measles, chickenpox, mumps. You may have experienced this phenomenon if you had a case of chickenpox. Vaccination spared you from getting any of those other diseases. In contrast, people of my generation all suffered chickenpox, measles, German measles, and mumps, but only once. What’s up with that? IMMUNOGLOBULINS 4/15/09 3 3 Introduction to Adaptive Immunity . IMMUNOGLOBULINS 4/15/09 4 4 Streptococcus pneumoniae bacteria were grown in the lab and about 50 bacterial cells were injected under the skin of 20 naïve adult mice. All the mice got sick and 18 out of 20 mice died within a few days. Studying Adaptive Immunity bacteria under It’s pretty remarkable that 50 little bacterial cells can cause the death of a mouse consisting of trillions of cells. Of course, during the infection, the original bacterial cells give rise to billions more by growing and dividing. We chose to inject 50 bacterial cells, because prior experiments established that this dose typically kills about 90% of the animals. A laboratory strain of mouse is highly inbred. The 20 animals are genetically nearly identical, so we can’t invoke that the two survivors are genetically resistant .
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IMMUNOGLOBULINS 4/15/09 5 5 Mickey and Minnie Mickey and Minnie were the two mice who survived infection with S. pneumoniae . Five weeks later, Mickey and Minnie were again injected with the same strain of S. pneumoniae , this time with about 150 cells per mouse. Mickey and Minnie did not get sick. Both of them survived, whereas 20 out of 20 naïve mice died within a few days after injection with the same number of bacterial cells. The 20 naïve mice are an experimental control to check that the bacteria we used on that day were virulent. Why did Mickey and Minnie survive? Why didn ! t they even get sick? IMMUNOGLOBULINS 4/15/09 6 6 Mickey and Minnie (continued) Mickey and Minnie were mated with each other and had 20 offspring, each of which was injected with about 150 cells of Streptococcus pneumoniae when they reached adulthood. All 20 offspring died within a few days after injection.
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