How is Blade immune to vampire bites?
When Blade’s mother was in labor, her friends summoned a doctor. Unknown to them, the doctor was also a vampire. The vampire (named Deacon Frost) attacked her during labor and somehow, the vampire’s blood mixed with Blade’s. This mixture caused an immune reaction which made Blade immune to being turned into a vampire. However he presumably could still die by blood loss, he just wouldn’t turn into a vampire.