This is my personal take on the mechanics vampirism.
A vampire has a symbiont/parasite living in its heart. This is why a stake to the heart is fatal, but many otherwise mortal injuries are recoverable. (Decapitation and fire kills most things, it's not a special vampire weakness)
This symbiont acts like a super liver/spleen/stem cell source (circulating symbiont stem cells in the vampires blood). Which provides super healing/long life abilities.
To turn a human to a vampire you need to drain almost all of the humans blood as the white blood cells defend against the invading symbiote [stem cells] in the vampire blood (which the vampire gives to their new 'child' to drink).
The symbiote provides many benefits, but has the drawback that silver and garlic are toxic to it. Also part of the essential nutrients it needs are found in blood. Which is why vampires have their peculiar diet. The stomach acid/enzymes are able to kill off any white blood cells they ingest. (So in theory you could kill a vampire by giving it a blood transfusion!) So they can and do still eat normal food, but it is not really a balance diet for them. So they need to supplement it with blood.
So to answer your question, vampire blood would not have any human white blood cells, but would have a an excess of super powered symbiote blood/stem cells.
Just so you know most blood work is done automatically/electronically these days. A drop of blood is viewed by a camera and uses image recognition to count the red blood cells and the different types of white blood cells. Humans have 5 different types of white blood cell. Some attack bacteria others attack parasites or cancer etc. A Dr. will look at the various white blood cell counts to help diagnose the the cause of an illness. So vampiric symbiosis could prevent one of these types (replacing it with its own) while ignoring the others. This might mean a Dr would misdiagnose a vampire as having Eosinophilia or Neutrophilia or something (those are just guesses you may want to ask a more specific question here or maybe on medical SE for plausible mis-diagnoses of vampirism when viewing a full blood count)
As to sun light I have two thoughts on how that would work:
- The circulating symbiote in the blood is sensitive to UV light which causes the release of toxins/intracelular enzymes, as they are damaged; and the loss of the vampires replacement immune system. Which leads to bad rapid sun burn, sloughing the of skin and in severe cases, necrotizing fasciitis.
- UV light doesn't directly harm vampires. They are pale and get sun burnt easily and have photophobia (bright light hurts their eyes), but those are just inconveniences; which modern sunscreen and fashionable glasses can deal with. However it does inactivate their vampiric abilities. So they lose their rapid healing and anti-ageing. This would mean going in the sun makes you get older, lose your youth and get one step further to dying of 'old age'. The more 'immortality' you have, the more you fear it being taken away from you.
Other vampire effects:
- The symbiote almost always causes infertility (the circulating symbiont can cross [testes|placenta]/blood barrier and fights off other 'invading parasites') So vampires can only reproduce symbiotically
- Hypnosis is not a thing, but they can produce pheromones which induce fear, relaxation, lust etc, in those near to them. (This is totally plausible, I know of people who get turned on, (and unconsciously sometimes start following the trail), if someone walking past them are wearing Fahrenheit by Christian Dior)
- A vampires bite, like wise, is venomous, injecting anti coagulants, pheromones, and healing accelerant factors. (From an evolutionary biology point of view, this means they can get close to their prey, get what they need, and get away without people (with pitch forks) noticing. This could even be beneficial to the victims; they have anemia and feel a bit woosie for a couple of days but get a temporary shot of healing and anti-aging serum! Sounds a good trade!