Assay: test or experiment
in vitro: in an artificial environment such as a Petri dish
isolate (noun): a strain of microorganism isolated from an infected individual or cell. Often used to refer to genetically distinct strains.
Leukopenia: low white blood cell count
lymph: immune system fluid. Can be used as a prefix, meaning pertaining to the immune system, as in lymphocyte.
Lymphadenopathy: abnormally small lymph nodes, usually because of a lack or lymphocytes
Morphological: pertaining to the shape of an organism
Peripheral blood lymphocyte: immune cells found in the peripheral blood, as opposed to those found in organs such as the spleen
Reverse transcriptase: enzyme found in retroviruses that synthesizes DNA from an RNA template
Serum: fluid portion of blood, containing salts, free proteins and other molecules, but not whole cells
Tropism: in immunology or pathology, the target cell or tissue for an infectious agent. Also as a suffix, as in lymphotropic.