Primary Hematopoietic and Lymphoid Tissue ›› Bone Marrow ›› Normal

Mature T-cells*






Microscopic Features:
  • Slightly (~1.5x) larger than a mature RBC
  • High nuclear to cytoplasmic ratio but with
  • Round mature Nucleus (clumped chromatin)
  • Nucleoli are absent
  • Cytoplasm is scant, light blue and lacks granules
Normal % blood-PB, marrow-BM, lymphoid tissue-LN:
  • PB: 2nd most common nucleated cell (WBC) in blood and most common lymphocyte in blood
  • BM: Scattered (<10%)
  • LN: Mainly scattered in Interfollicular areas of lymphoid tissue
May Resemble:
  • Mature B-cells (can't distinguish T-cell and B-cell based on morphology)
  • Orthochromic normoblast
  • Plasma cell (mature)
  • Reactive lymphocyte
  • Monocyte
Differential Diagnoses:

If increased in blood, Lymph node or bone marrow:
Infection
Neoplastic (mature T-cell lymphoma or leukemia)
Drug-induced
Autoimmune disorders
Idiopathic

Classic Immunophenotype:
  • CD2+
  • CD3+
  • CD4+ or CD8+
  • CD5+
  • CD7+
  • TCR+
  • TdT-
  • CD34-
Cartoon Image:



Misc:
  • Morphologically you cannot distinguish mature T-cells from mature B-cells In blood: There are more CD4+ T-cells than CD8+ T-cells (CD4:CD8 ratio is ~2-3:1) Majority of the mature T-cells express the Alpha/Beta TCR (only a small minority express the Gamma/Delta TCR)