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T Cell Analysis

Though the percentages of gated lymphocyte populations (T or B cells) are important, it is still necessary to determine if the cells present have a normal or abnormal CD marker representation. A population will also need to be scrutinized to evaluate whether it is 10% or 99% of the total lymphocytes.

Remember that lymphocytes will either be T cells or B cells and mature T cells will either be helper cells or suppressor/cytotoxic cells. With this in mind, normal mature T cells should express CD2, CD3, CD5, CD7, and either CD4 or CD8.

  • CD4 marks T-helper cells
  • CD8 marks cytotoxic T cells

The CD markers present in the peripheral blood sample in Case Two are:

  • CD2 = 17%
  • CD5 = 97%
  • CD7 = 17%
  • CD3 = 18%
    • CD4 = 10%
    • CD8 = 8%

Note the markedly increased CD5 percentage in relation to the other T cell markers. If this were a normal T cell population, it would have CD5 at roughly 17%.

In order to determine if the elevated CD5 percentage is due to abnormal T cells or to abnormal B cells that are marking with CD5, analyze a sample that has been stained with both CD5 and CD19 monoclonal antibodies. Two areas of interest would be CD5+ only and whether or not there is a CD19+/CD5+ dual marking population.

Note that on the image shown on the right, CD5+ only is 16.5% (rounds to 17%) and is in alignment with a normal T cell population in this sample.

T-cell analysis conclusion: T-cells are normal and the CD5+ cells that are also positive for CD19 represent abnormal B cells that express the T-cell marker, CD5.