BETA - What are white blood cells?

So the main job for white blood cells is to help you protect you from infections and also provide for the healing process in the context of a tissue injury. But of course, they can also be engaged in the context of things like cancer to try to eliminate a threat in that regard. The major white blood cell type, however, that we sort of think about when we think about white blood cells is something called neutrophils. And neutrophils are particularly relevant for helping fight bacterial infections. So the white blood cell count is important for infections. And especially the neutrophil count or the segmented neutrophils or whatever we call it or the ANC, they prevent us from having bacterial infections. It has been shown clearly that when your absolute neutrophil count or ANC is less than 500, your risk of infections, especially bacterial infections, increases rapidly. But it increases especially rapidly when it's under 200. So it's important to know what ANC is when you get on chemotherapy, because you know, now I'm starting to get at risk of having infections and I need to try to take all the preventative measures that I can to prevent having infections. Like I need to be careful with my food. I need to be careful with hand washing, that I don't touch anything, that I have no contact with people who have infections and things like that. White blood cells of course come in different flavors and different types. The most common type, if you will, is the neutrophil. The next more common type is what's called a lymphocyte. The lymphocyte is the one that gets classified into B lymphocytes or T lymphocytes. And also natural killer cells would fall into that same category. The third broad category of white blood cells would be things that would be classified as monocytes. And the other cell types are things like eosinophils and basophils, which are less common but have very distinct functions in specific situations like allergy or to fight parasitic infections, for example. So each cell type in the context of white blood cells performs a distinct role in our bodies as a physiologic role. So there are many different types of white blood cells. Are in a way the most important ones and really probably the only important ones, although I hesitate to ever say that to our myeloma patients, are their neutrophils and their lymphocytes. The monocytes are often the first blood cell when the bone marrow is recovering. And so in the peritransplant period, we may see those come up shortly before the neutrophils start to come up. But basophils, eosinophils, and monocytes really are not important to myeloma patients. They're very important in other blood disorders and other situations. But those are ones you can probably disregard. The neutrophils are the most important. The lymphocytes have value too, but the neutrophils are the most important. The monocytes are kind of important because they're usually the first cells to come back. So when you see your differential that the monocytes are going up, then you know the neutrophils will come next. And that's why we use it mainly. The basophils, they tell us whether there is some kind of allergic reaction, just like the eosinophils. They are mainly involved in basophils in the release of histamine and the eosinophils in the body. And then we have the lymphocytes, which are the most important. The lymphocytes are important because they're the most important part of our immune system. In addition to bacterial infection, we're also exposed to infections such as viral infections or other types of opportunistic type of infections that normally are not a problem at all if we have a good immune system, but can become a problem if our immune system is down. And in the lymphocytes, we distinguish two types of cells. One is the T cell and the other one is the B cell. And the T cells, they prevent us from having infections such as cytomegalovirus. The antibodies, they will prevent us from having some viral infections. So they are both important. And one should remember that it's not because your neutrophil count is back into a safe range that your immune system is normal. Normally it takes a much longer time after heavy chemotherapy to have the immune function back to normal. Typically about four to six months after the last transplant before the immune function is good enough to say, well, now we can really be a little less careful and we can do whatever we want to do. The neutrophils are your primary defense against bacteria and they are the ones that we follow the most closely. Lymphocytes tend to be more important for viral and fungal type infections, but they are important as we think about things that are with regard to lymphocyte therapies and some of our engineering treatments such as CAR T cells and things that are coming about. But they're not ones that tend to change that much with treatment. It's really the neutrophils that tend to go down and then back up again in response to treatment the most predominantly. When you have low neutrophils, it's what we call neutropenia, especially when those cells are less than 500. So you may hear the team talking about you being neutropenic or neutropenic fever precautions. Those are implemented when that neutrophil count is low. And again, especially if it's less than 500, but oftentimes when it's less than a thousand, we will be of concern and consider making adjustments again, depending on the patient in the clinical situation. Well, the one that I looked the most at is the CD4 count. And when the CD4 count is under 200, we are at extreme high risk of infections. When it's between 200 and 500, the risk decreases. And when it's over 500, things are okay. The most important is absolute neutrophil count. You can have 60% neutrophils, but the total white blood cell count is only 0.2. And you're still going to have a very low absolute neutrophil count. You can have 30% neutrophils, but total white blood cell count is 10,000, and you're going to be good. So again, the absolute neutrophil count is what is the most important. And once that's over a thousand, your risk of bacterial infections decreases rapidly. So when we have a low white blood cell count, we typically will give prophylactic antibiotics. These are oral medications that decrease the risk of infection. And the most commonly used are quinolones, either levacuin or Cipro are the most commonly used. Also, at some point in time, when you think that the bone marrow is starting to get into function again, then you can give growth factors such as Nulasta or GCSF, Nupogen, to stimulate the white blood cells and let them come back earlier. But there is in general no reason to give those drugs too early when there is nothing to stimulate. You need to wait until there is some chance that the bone marrow function is recovering. And that is usually around day six after a transplant or about day six after heavy chemotherapy. Well, it depends if you are on heavy chemotherapy to collect your stem cells, for example, or after a transplant, you know this is going to happen and this is unavoidable. Your counts will go down to almost zero. However, if you are on maintenance therapy, you don't want to have your white blood cell count go too low. And if you see that the white blood cell count goes too low, you will decrease the doses of the chemotherapy to make sure that people do not drop their white blood cell count too low and that their ANC does not go under 500 and preferentially not under 1000.