Clonal expansions of V delta 1+ and V delta 2+ cells increase with age and limit the repertoire of human gamma delta T cells

We have investigated the complexity of the human gamma delta T cell repertoire by means of a VJ heteroduplex analysis method. cDNA obtained from peripheral blood mononuclear cells was amplified with V delta 1-C delta or V delta 2-C delta primers. The product was denatured and renatured to allow random reannealing of the strands and the heteroduplexes carrying mismatched junctional sequences were separated from the homoduplexes on polyacrylamide gels. Whenever one or more T cell clones were expanded to over 10% of the polyclonal background, discrete bands of homo- and heteroduplex appeared. This method was applied to the analysis of the peripheral gamma delta compartment from healthy donors and rheumatoid arthritis patients of different ages. While samples from young individuals showed a polyclonal pattern, a clear tendency towards oligoclonality appeared with increasing age, both in normal individuals and rheumatoid arthritis patients. We also show that the VJ junctional sequence derived from the heteroduplex fragments can be successfully used to isolate and characterize the corresponding T cell clones in vitro, even after a period of 1 year. In conclusion, our findings indicate that the complexity of the gamma delta T cell repertoire decreases with age as a consequence of the expansion of a few T cell clones.

T cell receptor heterogeneity in gamma delta T cell clones from intestinal biopsies of patients with celiac disease

In celiac disease large numbers of gamma delta T lymphocytes infiltrate the intestinal epithelia. We have isolated intestinal gamma delta T cell clones from patients with celiac disease and have analyzed their T cell receptor repertoire. T cell lines and clones were obtained from jejunal biopsies of 14 celiac patients and 12 individuals without celiac disease. These were analyzed by staining with monoclonal antibodies against CD3, alpha beta and gamma delta T cell receptor, by Southern blot with gamma- and delta-specific probes and by polymerase chain reaction using V delta-specific oligonucleotides. Intestinal gamma delta cells from patients with celiac disease differed from those of controls with normal jejunal histology in that V delta 1+ cells and V delta 1-V delta 2- cells were significantly increased. There was no evidence of the expansion of one or more clones expressing particular types of gamma delta T cell receptor.

Unique genotypic features of infant acute lymphoblastic leukaemia at presentation and at relapse

Acute lymphoblastic leukaemia (ALL) of infants aged less than 1 year represents a group of patients with peculiar biological features, poor response to therapy and unfavourable prognosis. In order better to characterize this type of leukaemia, we have investigated the immunoglobulin (Ig) and T-cell receptor (TCR) genes configuration of 21 infants with ALL, and compared the genotypic features with the phenotypic and karyotypic data, as well as with the clinical outcome. All cases had a pre-B phenotype; 12 (57%) of them were pre-pre-B ALL (CD10-, CD19+). Six of the 16 cases evaluated (38%) displayed chromosomal abnormalities; five had the typical translocation t(4;11)(q21;23). Eleven cases presented with a white blood cell count greater than 100 x 10(9)/l. The clinical course was unfavourable in 14 patients. The genotype of this group of ALL revealed several peculiarities. (1) Of the 21 cases, six (29%) displayed a multiple rearrangement pattern at the IgH locus. (2) In three cases (15%), the light chain genes were rearranged. (3) The TCR beta and gamma genes were rearranged in only one case (one case at the TCR beta and one at the TCR gamma locus). (4) The TCR delta chain was rearranged in eight cases (40%) and rarely deleted; the rearrangements observed were those most frequently observed in B cell-precursor ALL. Two cases were evaluated both at presentation and at relapse. While the immunophenotype had remained unmodified, comparison of Ig heavy chain gene rearrangements revealed clonal variations in both cases. Taken together, these findings further underline the biological peculiarities of infant ALL compared to ALL which occurs in older children and in adults, and stress the need of differentiated and aggressive therapeutic approach for these patients.

Selection by two powerful antigens may account for the presence of the major population of human peripheral gamma/delta T cells

V gamma 9/V delta 2 cells represent a fraction of human gamma/delta cells that is expanded after birth in the periphery, carries markers of activated cells, and becomes a major population in peripheral blood. We found that these cells do not comprise a single population but actually represent two nested sets, the smaller of which, specific for Mycobacterium tuberculosis-pulsed antigen-presenting cells (APC), is contained in a larger set specific for an antigen found on the Molt-4 lymphoma. The larger set, representing 40-80% of all blood gamma/delta cells, is comprised of cells bearing the V gamma 9/C gamma 1 chain. Cells in the smaller, included set have an additional requirement for V delta 2 (and probably for certain permissive junctional regions, since a very small percentage of V gamma 9/V delta 2 cells do not react against mycobacteria-pulsed APC). Optimal stimulation by mycobacteria is dependent on the presence of APC, and is not restricted by classical major histocompatibility complex molecules. Some of the V gamma 9/V delta 2 mycobacteria-specific clones are also stimulated by APC pulsed with different bacteria, such as Listeria monocytogenes and Escherichia coli, indicating that the population includes several different patterns of reactivity. These data establish a relationship in humans between specificity and V gamma/V delta gene usage, and offer an explanation for the peripheral expansion of these gamma/delta cells.