Lymphoma and plasma cell neoplasms
Lymph nodes
Normal lymphocyte development - T cells

Author: Nikhil Sangle, M.D. (see Authors page)

Revised: 3 April 2017, last major update January 2011

Copyright: (c) 2001-2017, PathologyOutlines.com, Inc.

PubMed Search: t cells lymphocyte development lymphoma

Cite this page: T cells. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/lymphomanormalTcells.html. Accessed June 29th, 2017.
Definition / general
  • Develop from bone marrow, become prothymocytes, then migrate to thymus gland, where self recognizing T cells are eliminated
Pathophysiology
  • T cell receptors (TCR) are either alpha / beta (95%) or gamma / delta (5%) heterodimers
  • T cell progenitors migrate to the thymus and undertake a highly ordered developmental program, regulated by signals derived from microenvironment
  • Most immature thymocytes are CD4- / CD8- ("double negative" / DN); DN is divided into 4 stages based on CD44 / CD25 expression: DN1 is CD44+, CD25-; DN2 is CD44+, CD25+; DN3 is CD44-, CD25+; DN4 is CD44-, CD25- (Immunol Res 2010;47:45)
  • Precursor cell is TdT+, CD34+, HLA-DR+, then drops HLA-DR, then adds CD2, CD5, CD7 (early thymocyte) while undergoing gamma / beta chain rearrangement, then adds CD1 and drops CD34, now a common thymocyte (CD4-, CD8-, "double negative"), then undergoes beta / alpha chain rearrangement (DN3 stage) and adds CD4 and CD8, then splits into helper (CD4) or cytotoxic (CD8) T cell ("single positive") with CD2 and CD3, and without TdT, CD1, CD5 and CD7
  • T alpha and delta genes are on 14q11; T beta gene is on 7q34; T gamma gene is on 7p15
  • Note: T cells and NK cells arise from common progenitor that expresses CD3 epsilon and cannot develop into B cells
Diagrams / tables

Images hosted on PathOut server:

T cell biomarker
expression during
development (AFIP)



Images hosted on other servers:

T cell activation

T cell development

Clinical features
  • 90% of peripheral T cell lymphomas have rearrangements of T alpha, beta and gamma, including all cases of mycosis fungoides and Sezary syndrome
  • T cell lymphomas have no distinct marker of clonality, but cells may express an abnormal immunophenotype or TCR gene rearrangement
  • As there are only 10 V (variable) regions, a polyclonal population of cells can appear oligoclonal
  • T cell clonality is seen in AIDS and congenital immunodeficiency syndromes, but does NOT indicate malignancy
  • Rarely a clonal band may comigrate with the germline band; solution: use 2 - 3 restriction enzymes (HindIII, EcoRI, BamHI)
Positive stains
Negative stains
Videos


T Cell Development