chapter 3.docx

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Department
Biochem. and Medical Genetics
Course
BGEN 3020
Professor
Jason Leboe- Mcgowan
Semester
Fall

Description
Chapter 3 Blood Groups Different blood groups and what is floating around in the serum: O is most common, A is 2 most nd rd common, B is 3 common, and AB is the rarest O: have anti-A IgM, anti-B IgM, anti-AB IgG A: anti B IgM B: anti A IgM AB: nothing Newborn: nothing, why? They don’t begin synthesizing IgM until after they are born and only after 2-3 months do they start synthesizing IgG. Elderly: nothing – Example: an old person who is blood group A and by mistake received blood group B, but did not develop a hemolytic transfusion rxn – why? Their levels of Ab’s are low when they get older that there wasn’t anything around to attack those cells. Associated Diseases: Which is associated with gastric cancer? A Which is associated with duodenal ulcer? O Universal donor? O (can give their blood to anyone b/c have NO anti-A or anti-B Ag). What is the only blood group O can get? O Universal recipient? AB b/c they have no Ab’s to attack those cells Other Antigens: 1. Rh + antigen means that you are “+” for D antigen 2. Duffy Ag is missing in black pop’n; therefore not as likely to get plasmodium vivax (malaria) b/c the Ag the P. vivax needs to parasitize the RBC’s is the Duffy ag and if you don’t have the Ag the P. vivax can’t get it. (G6PD def, thalassemias, SCDz pts protected from falciparum – they are protected b/c they’re RBC’s have a shorter lifespan – so, the parasite cannot live out their cycle, and RBC’s a shorter lifespan) Major crossmatch: pt gonna get blood; their serum is in a test tube, with the blood of the donor unit and they mix the 2 together – so they mix the pt’s serum with the donor’s RBC’s to see if they are compatible; looking for anything in the pts serum that will attack the antigens in the donor’s RBC’s. Another part of the workup for crossmatching is to do an antibody screen which is an indirect coomb’s before mixing (remember that it detects the ANTIBODY). If this test is negative, the crossmatch is compatible (so, there is no Ab in the pts serum that will attack the donor’s). This does not prevent a transfusion rxn, or that Ab’s will develop later against the donor. What is the chance that anyone has the same Ag makeup as another? Zero. So, even if I get a blood group O when I’m group O, there is still an increase risk of ab attack. Moral of the story? Don’t transfuse unless it’s absolutely necessary Audio Day 3: hematology 8 Side Notes A. Questions asked during the break about hypersensitivity: Lupus (not everything is type III) Post strep (not everything is type III, either) – can cause type II if its post strep. rheumatic fever, however, if it is post strep glomerulonephritis, that is type III Thrombocytopenia and Hemolytic anemia = type II PCN rash = type I PCN hemolytic anemia = type II (IgG Ab’s against the PCN group attached to the RBC membrane) Example: most common Ab in the USA is Anti-CMV (everyone has been exposed). You are safest from getting HIV from blood transfusion than from all the other infections (1/625,000 per unit of blood chance of getting HIV– therefore uncommon get to get HIV from blood). This is due to all the screening tests that they perform. They do the Elisa test – which looks for anti-gp120 Ab’s (remember, it’s the gp-120 Ag that attaches to helper T cell (CD4) molecule). On western blot, looking for more (3 or 4) Ab’s, making it more specific, so if you get this “+” on 3 or more, you are a true positive. . What is the MC infection transmitted by blood transfusion? CMV, which is the MC overall infection. That is why this antibody is the most common. What is MCC post transfusion hepatitis? Hep C (1/3000) In newborn, want to prevent graft vs. host dz and CMV b/c no immune defenses, therefore, need to irradiate the blood. The irradiation kills off the lymphocytes and since the CMV lives in lymphocytes, we kill off the CMV virus also. This why we radiate blood before giving to newborns. Accidental needle stick from a pt you know nothing about – what is the MC infection you can get? Hep B. Accidental needle stick from HIV “+” pt; what is the chance of getting HIV+? 1/300. What do you do about it? You go on therapy as if you are HIV+. Go on to triple therapy (2 RTI’s – AZT and a protease inhibitor) for six months and get constant checks – do PCR test looking for RNA in the virus (most sensitive), do Elisa test. In fact, the MC mechanism of a healthcare worker getting HIV = accidental needle stick Do not transfuse anything into a person unless they are symptomatic in what they are deficient in. Example: If you have 10 grams of Hb, and have no symptoms in the pt, do not transfuse. You should transfuse the pt if they have COPD and are starting to have angina related to the 10 grams.
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