T cells, on the other hand, are responsible for orchestrating the immune response and are also one of the cells which can attack foreign particles. They are helpful in eliminating viruses and tumor cells in the body by binding directly to antigens on these organisms and tumor cells. Unlike B cells, T cells do not secrete antibodies.
There are many, many T and B cells in the body. These cells circulate throughout the body, passing through lymph nodes and the spleen, as they look for "foreign" antigens to which they can react. Once they find an antigen, the lymphocytes become "stimulated" and divide rapidly to make other cells. If these stimulated cells are B cells, they also turn into plasma cells and begin secreting antibodies.
During an infection or other threat, many different B cells and T cells can recognize different pieces of an antigen, causing each of them to proliferate. This results in many large groups of T and B lymphocytes. The end result is a lot more lymphocytes, which can cause lymph nodes (the place where lymphocytes congregate) to enlarge. This is why swollen "glands" (which are lymph nodes), often mean an infection is present.
