Structure of T Cell Receptor Vα and Vβ Chains Expressed by T-Lymphocytes in Cardiac Allograft Derived Cell Lines

Rearrangements of the T-cell receptor (TCR) delta locus are observed in the majority of human B-cell precursor acute lymphoblastic leukemias (ALL) with a striking predominance of V delta 2(D)D delta 3 recombinations in common ALL (cALL) patients. Recently, we and others showed that almost 20% of cALL cases are characterized by further recombination of V delta 2(D)D delta 3 segments to J alpha elements, thereby deleting the TCR delta locus in analogy to the delta Rec/psi J alpha pathway in differentiating alpha/beta-positive T cells. We report here that two human cALL-derived cell lines, REH and Nalm-6, are competent to recombine the TCR delta/alpha locus under standard tissue culture conditions. Analysis of different REH subclones obtained by limiting dilution of the initial culture showed a biased recombination of V delta 2D delta 3 to distinct J alpha elements. During prolonged tissue culture, a subclone acquired growth advantage and displaced parental cells as well as other subclones. Frequently, the DJ junctions of REH subclones contained extended stretches of palindromic sequences derived from modified D delta 3 coding elements. The other cell line, Nalm-6, started the TCR delta/alpha recombination with an unusual signal joint of a cryptic recombinase signal sequence (RSS) upstream of D delta 3 to the 3′ RSS of D delta 3. The RSS dimer was subsequently rearranged in all investigated subclones to an identical J alpha element. Both cell lines might become valuable tools to unravel the complex regulation of TCR delta/alpha recombination pathways in malignant and normal lymphopoiesis.

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Circulating CD8 T Lymphocytes in Human Immunodeficiency Virus-Infected Individuals Have Impaired Function and Downmodulate CD3ζ, the Signaling Chain of the T-Cell Receptor Complex

Blood ◽

10.1182/blood.v91.2.585.585_585_594 ◽

1998 ◽

Vol 91 (2) ◽

pp. 585-594 ◽

Cited By ~ 2

Author(s):

Linda A. Trimble ◽

Judy Lieberman

Keyword(s):

Human Immunodeficiency Virus ◽

T Cells ◽

T Cell ◽

T Lymphocytes ◽

T Cell Receptor ◽

Cell Receptor ◽

Receptor Complex ◽

Cd8 T Lymphocytes ◽

Immunodeficiency Virus ◽

Specific Cytotoxicity

Although human immunodeficiency virus (HIV)-infected subjects without acquired immunodeficiency syndrome have a high frequency of HIV-specific CD8 T lymphocytes, freshly isolated lymphocytes frequently lack detectable HIV-specific cytotoxicity. However, this effector function becomes readily apparent after overnight culture. To investigate reasons for T-cell dysfunction, we analyzed T-cell expression of the cytolytic protease granzyme A and of CD3ζ, the signaling component of the T-cell receptor complex. An increased proportion of CD4 and CD8 T cells from HIV-infected donors contain granzyme A, consistent with the known increased frequency of activated T cells. In 28 HIV-infected donors with mild to advanced immunodeficiency, a substantial fraction of circulating T cells downmodulated CD3ζ (fraction of T cells expressing CD3ζ, 0.74 ± 0.16 v 1.01 ± 0.07 in healthy donors; P < .0000005). CD3ζ expression is downregulated more severely in CD8 than CD4 T cells, decreases early in infection, and correlates with declining CD4 counts and disease stage. CD3ζ expression increases over 6 to 16 hours of culture in an interleukin-2–dependent manner, coincident with restoration of viral-specific cytotoxicity. Impaired T-cell receptor signaling may help explain why HIV-specific cytotoxic T lymphocytes fail to control HIV replication.

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