So many blood groups #A+, A-, B+, B-, AB+, #AB-, #O+, O- 
Kaise pata chalega, mere blood group ke saath kaun sa blood group #compatible hoga. 
Woh complicated charts ke permutations and combinations ko kaise yaad rakhein. 
What is the role of my #immune system in blood group incompatibilities?
Who can be a #universal #donor?  
Who can be a universal recipient? 
The letters and +ive and -ive sign in the name of your blood. Two different blood groups will be compatible only if the #antigens of the incoming blood match exactly with those of the receiver. If their antigens do not match, the red blood cells of the incoming blood will be clumped by the receiver's immune cells and clots will form indicating that the two bloods are not compatible.