Terminal deoxynucleotidyl transferase-positive cells in human tonsils

Area of Science:

• Immunology
• Cell Biology
• Pathology

Background:

• Recent recognition of indolent TdT-positive T-lymphoblastic proliferations in tonsils and oropharynx.
• Uncertainty regarding the cellular origin of these proliferations.

Purpose of the Study:

• To investigate the presence and phenotype of TdT-positive cells in normal human tonsils.
• To determine if tonsils are a site of lymphopoiesis.

Main Methods:

• Immunohistochemical staining of normal human tonsils from children and adults.
• Double-antibody staining to determine cell phenotype.
• Comparison with reactive lymph nodes as controls.

Main Results:

• TdT-positive cells were readily found in tonsils, distributed in discrete foci.
• These cells exhibited the phenotype of uncommitted early lymphoid precursors (CD3-, CD79a-, CD10-).
• TdT-positive foci were absent in control reactive lymph nodes.

Conclusions:

• Human tonsils harbor TdT-positive lymphoid precursor cells, similar to bone marrow and thymus.
• Tonsils are identified as sites of lymphopoiesis.
• The presence of these precursor cells may play a role in the pathogenesis of tonsillar T-lymphoblastic proliferations.