<unk>  is a procedure that is performed prior to in vitro fertilization, in order to use<unk> s with maximal chances of resulting in pregnancy. In contrast, embryo<unk>  takes place after fertilization. __TOC__
Oocyte selection
Antigen presentation
Lymphopoiesis
Alloantigen recognition
Affinity maturation
Receptor editing
Immune cycle
Apoptosis