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

Increased Mature T-cells*


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› Microscopic Features:

• Slightly (~1.5x) larger than a mature RBC (activated T-cells may be 2-3x the size of a normal 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 [Compare]
• Plasma cell (mature) [Compare]
• Reactive lymphocyte [Compare]
• Monocyte [Compare]

› 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:


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for direct comparison
› 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)