More recently, monoclonal antibodies have been developed to
identify and enumerate T and B lymphocytes.5,6 Compared to
the relatively nonspecific polyclonal antibodies (heteroantisera)
produced against these cellular populations, monoclonal
antibodies define specific, discrete T-cell and B-cell surface
antigens. This allows not only for more accurate and precise
lymphocyte measurements but in conjunction with other cell
markers (TdT, HLA-D related antigen, SmIg) for identification
of distinct stages of T-cell and B-cell differentiation.
Cell surface antigens appear to be acquired and lost by T
and B lymphocytes in a manner reflecting the maturational
(differentiation) and/or functional state of the cell. Once
acquired, the same cell may coexpress some or all of
these antigens for varying periods of time.