Question

memorization fact: in addition to abo, there is another component of blood type - the rh factor. people who posses rh antigens are referred to as rh positive (e.g. o+ have neither a or b but they do have rh), people without rh antigens are rh negative (a- would have the a antigen but not b or rh).
model 3: erythroblastosis foetalis (a disease in which a pregnant womans anti-rh antibodies destroy fetal red blood cells and typically results in miscarriage).
woman with rh negative blood type is pregnant with an rh positive baby
mother produces no anti-rh antibodies at the beginning of pregnancy, but she is exposed to fetal rh antigens
after being exposed to the rh antigen, mother is now sensitized and produces anti-rh antibodies
any subsequent exposure results in the anti-rh antibodies destroying all rh-positive cells
critical thinking questions:

1. dr. brown has the blood type a negative. according to the model and the memorization fact, to what antigen does the word

egative\ refer?

1. compare the first pregnancy with the second, does it appear that the first baby was affected by the mothers immune system? what triggers the mothers sensitivity to the rh antigen?
2. based on the model, if dr. brown has never been exposed to the rh antigen, what do you think will happen if he is transfused with a positive blood?
3. what will happen if he is transfused with a+ blood a second time?

brief explanations:
a. model 1 explicitly lists four distinct blood type columns for humans.
b. observing the \cell with attached antigen\ row for type a, the a antigen is a circle with triangular spikes.
c. comparing type a and type b red blood cells in model 1, the key difference is the specific antigen on the cell surface and the corresponding antibody produced.

Explanation:

1. Per the memorization fact, "negative" in blood type means the absence of Rh antigens; Dr. Brown's A negative has A antigens but no Rh antigens.
2. Model 3 shows the first pregnancy has no pre-formed anti-Rh antibodies, so the fetus is unharmed. Sensitivity comes from exposure to fetal Rh-positive blood (likely during delivery) which stimulates antibody production.
3. As an Rh-negative person with no prior Rh exposure, transfusion with Rh-positive (A+) blood will trigger the immune system to make anti-Rh antibodies, which then attack the foreign Rh-positive cells.
4. After the first exposure, anti-Rh antibodies are already present. A second transfusion of Rh-positive blood will immediately trigger these antibodies to destroy the transfused cells, leading to a severe transfusion reaction.

Answer:

1. The "negative" refers to the absence of the Rh antigen.
2. No, the first baby was not affected. Sensitivity is triggered by exposure to fetal Rh-positive blood during the first pregnancy/birth.
3. Dr. Brown's immune system will start producing anti-Rh antibodies, and the transfused Rh-positive blood cells will be destroyed.
4. The pre-existing anti-Rh antibodies will rapidly attack and destroy the transfused Rh-positive blood cells, causing a severe, potentially life-threatening reaction.