Re: Could white blood cells be grow to help fight viral diseases?

Not only is part of your answer a possibility for the future, it is a
possibility right now. Antibodies are routinely used for what is called
"passive-vaccination" to protect against a number of  medical problems.
Anti-venom, used to treat snake bites, is literally antibody generated
against snake venom (usually in horses). The development of monoclonal
antibodies in the 70s has led to a revolution in pharmaceuticals. A number
of new pharmaceuticals are based on specially designed and modified
antibodies, including treatments for the damage caused by heart attacks.
Antibodies are also employed as one of several new means for fighting cancer.

While antibodies are useful for treating sick patients it is a different
story for T cells. First, the patient and donor would have to be a perfect
MHC match in much the same way that patients are matched with donors for
organ transplants. T cells have been taken from cancer patients, grown in
culture and re-injected to help fight cancer with mixed results.

For viral or bacterial disease, however, it won't work. T cells take time
to grow in culture to sufficient numbers - and for most diseases the
outcome will have been decided before sufficient numbers of cells are
available. That is true whether you use T cells from the patient or an
MHC-matched donor. Our own bodies are currently far more capable of
expanding T cells to fight disease than we can do in culture.

Of course it is difficult to predict the future and there may come a time
when it is feasible to grow T cells in culture and inject them into the
patient. Antibody is already there and working wonders.