Investigation of the clonality of lymphocytes in Hashimoto's thyroiditis using immunoglobulin and T-cell receptor gene probes

Clonal B cell populations in a minority of patients with Hashimoto's thyroiditis

BACKGROUND

Hashimoto's thyroiditis (HT) is a risk factor for thyroid lymphoma, and clonal B cell populations in HT support this link. The literature on B cell clonality in HT is controversial.

AIMS

To identify clonal B cell populations in HT and to assess their usefulness in differentiating HT from mucosa associated lymphoid tissue (MALT) lymphoma and predicting future development of lymphoma.

METHODS

DNA from formalin fixed, paraffin wax embedded blocks of thyroid specimens from 10 patients with HT and two thyroid MALT lymphomas was analysed for B cell clonality by seminested polymerase chain reaction (PCR) using FRIII/LJH and FRIII/VLJH primers to amplify the IgH gene VDJ region. In one case, PCR products were sequenced. Immunohistochemistry was performed by labelled streptavidin-biotin technique using antibodies to: CD45, CD45RO, CD3, CD20, and cytokeratin.

RESULTS

The histopathological and clinical findings were characteristic of HT. Clonal bands were seen in three and a polyclonal smear pattern was seen in seven cases. The clonal bands in HT were associated with a background smear, and could not be reproduced from other blocks from the same case or from deeper sections of the same block. The clonal bands in thyroid lymphomas were not associated with a background smear and were reproducible. None of the patients with clonal B cells has developed malignant lymphoma during a follow up of 10-13 years.

CONCLUSIONS

B cell clonal bands in HT have different features from those in lymphoma (non-pure and non-reproducible) and do not predict future development of lymphoma.

T-cell receptors and autoimmune thyroid disease--signposts for T-cell-antigen driven diseases

The human autoimmune thyroid diseases (AITDs) are characterized by profuse infiltrates of both CD4+ and CD8+ T cells. The intrathyroidal T-cell-receptor repertoire in Graves' disease, more than in Hashimoto's disease, has been shown to be biased as evidenced by phenotypic analysis and by the use of a restricted T-cell-receptor variable (V) gene repertoire seen in both TCR alpha and beta chains. Evidence for a bias in the T-cell repertoire has also been observed in animal models of induced and spontaneous autoimmune thyroiditis. We found a similar phenomenon of autoimmune thyroid-related T-cell bias in thyroid-humanized scid mice. In these studies we transplanted lymphocyte-depleted thyrocytes and autologous peripheral lymphocytes from AITD patients with a basement membrane preparation which allowed the formation of an artificial thyroid which we have called an "organoid". T-cell clonal expansion was present in these artificial mixed-cell organoids which appeared to mimic the in vivo process. Such clonal expansion was suggestive of an antigen-driven immune response and could also be identified in thyroid tissue from patients with Graves' disease. Our data on scid mice grafted with human mixed-cell thyroid organoids, therefore, suggested that the major antigens driving T-cell selection in patients with AITD were most likely to be thyroid specific. These antigens include thyroglobulin, thyroid peroxidase, and the receptor for thyroid stimulating hormone (TSHR) on the surface of thyroid epithelial cells and we found significant T-cell proliferation to synthetic TSHR peptides in patients with AITD as compared with normals. Our search for a TCR recognition motif for the autoantigen TPO did not reveal any specific sequence motifs. Instead, analysis of the physico-chemical characteristics i.e. hydrophobicity of the amino acids in the CDR3 (N) region of the TCR alpha chain, revealed a strong negative linear correlation between strength of stimulation and the average hydrophobicity of N-region amino acids. This led us to hypothesize that lower affinity T-cell clones were commonly more hydrophobic in their CDR3 alpha region amino acids in keeping with potential crossreactivity of such T cells as a consequence of promiscuous, hydrophobic CDR3 regions. This phenomenon would be analogous to polyreactive, natural autoantibodies which tend to be crossreactive and 'sticky'. Thus, the physico-chemical characteristics of the TCR alpha CDR3 region supported the interaction with antigen/MHC by potentially cross-reactive T cells of low affinity. It would seem likely that such low-affinity autoreactive T-cell populations serve as a pool of potentially pathogenetic cells. These cells would be able to respond to an insult which, via a number of possible mechanisms such as molecular mimicry, would initiate a thyroid lymphocytic infiltration in an antigen-driven fashion with intrathyroidal T-cell expansion and a marked bias in the utilization of T-cell-receptor V genes.

Preservation of functioning human thyroid "organoids" in the scid mouse. IV. In vivo selection of an intrathyroidal T cell receptor repertoire

To study the in vivo influence of thyroid cells on the T cell receptor repertoire in human autoimmune thyroid disease, we mixed lymphocyte-free thyrocytes (approximately 1.2 x 10[6]) from patients with Graves' disease with autologous peripheral blood mononuclear cells (PBMC; approximately 1.5 x 10[6]) and transplanted this mixture sc into scid mice while suspended in a basement membrane gel (approximately 0.4 ml). Controls included mice that received either thyrocytes only or PBMC only. The resulting artificial mixed cell thyroid organoids were explanted after 5 weeks, and their T cell receptor repertoire was examined. Of a total of 63 organoids constructed, 60 were recovered (95.2%). Total RNA was extracted and then analyzed by reverse transcription-PCR primarily for human T cell receptor (hTcR) Vbeta gene expression using 21 hTcR Vbeta amplimers. A restricted pattern of hTcR Vbeta gene expression was found, with 6 Vbeta genes (Vbeta5, 6, 7, 8, 13.1, and 18) predominantly expressed [P < 0.05, by ANOVA on ranks and Student-Newman-Keul's (SNK) test]. PBMC and control organoids showed no preferential selection of particular hTcR V gene-expressing T cells. This reductionist, mixed cell, thyroid model reflected earlier observations in human and murine autoimmune thyroid diseases in which a bias in hTcR V gene family expression had been observed. The model permitted in vivo T cell selection and/or enrichment of potentially disease relevant human T cells.

Immunological mechanisms in atherosclerosis

Immunological mechanisms seem to be potent modulators of the atherosclerotic process. The presence of substantial numbers of T-lymphocytes in the lesion and local and circulating autoantibodies to plaque components suggests that a specific immune response is operating. Focal expression of adhesion molecules and local secretion of chemoattractants could mediate the recruitment of inflammatory cells to the lesion. Local cytokine and growth factor networks may operate later, controlling cell migration and proliferation. Although it is still important to realize the complexity of these mechanisms, the ongoing characterization of the molecular mechanisms in atherogenesis may lead to new strategies for intervention with the disease process.

Infections and autoimmune endocrine disease

The literature examined in this review points to the possible involvement of infectious agents in the pathogenesis of autoimmune endocrine diseases, primarily autoimmune thyroid disease and diabetes mellitus. Various mechanisms have been proposed to explain induction of autoimmunity by infection but it seems that three possibilities may be important in individuals susceptible to developing autoimmune disease: molecular mimicry (perhaps to retroviruses); polyclonal T cell activation (by an endogenous superantigen or an infecting organism); and MHC class II antigen induction. It seems reasonable that all three mechanisms operate together or separately in different individuals. Data continue to accumulate in favour of infectious agents being important initiators of autoimmune disease.

Increased natural antibody activity in sera of patients with malignant non-Hodgkin's lymphomas containing paraproteins

In view of the frequent association between malignant lymphoproliferative diseases and autoimmunity, we studied by ELISA the presence, isotype, and specificity of natural antibodies in sera from 60 patients with malignant non-Hodgkin's lymphomas and 70 healthy controls. The antigens selected were actin, tubulin, myosin, troponin, tropomyosin, keratin, thyroglobulin, single stranded DNA, and the hapten trinitrophenyl. The results of this study were compared with the presence of oligoclonal immunoglobulins in the same sera, as previously detected by Isoelectric Focusing and Immunoblotting. Our results showed that 1) there is a high proportion of autoreactive NHL sera: 28 (46.6%) exhibited high IgG natural antibody activity (Nab) against one or more panel antigens, mostly against keratin, myosin, and tropomyosin, 26 (43.3%) had high IgA Nab activity, mainly against myosin, keratin, and ssDNA, whereas 17 (28.3%) displayed a high IgM Nab activity. The great majority (> 80%) of positive sera was polyspecific, i.e., reacted with at least two panel antigens. 2) A strong correlation exists between the high serum Nab activity and the presence of paraproteins: of the 28 sera exhibiting high IgG Nab activity, 16 (57%) contained oligoclonal IgG, and of the 17 sera exhibiting high IgM Nab activity, 13 (76.4%) contained oligoclonal IgM. The Nabs detected had frequently the same heavy and light chain as the paraproteins. No relationship between the presence of paraproteins with Nab activity and the stage of disease or grade of malignancy was found. We conclude that the high incidence of clonal immunoglobulins of different isotypes with various autoantibody specificities suggests an oligoclonal lymphocyte activation involving Nab producing cells. The significance of such autoreactive clones in NHL patients remains to be elucidated.

Immune mechanisms in atherogenesis

Research in recent years has resulted in an increased understanding of the molecular mechanisms in the development of inflammatory processes. In atherosclerosis, focal expression of key adhesion molecules has been detected which may mediate the recruitment of mononuclear cells to the plaque. Local cytokine production could account for further cell migration and proliferation. The presence of substantial numbers of T lymphocytes in the plaque and local and circulating autoantibodies to modified lipoproteins suggest that T and B lymphocyte responses may play important roles in these processes.

No restriction of intrathyroidal T cell receptor V alpha families in the thyroid of Graves' disease

Recently it has been reported that the intrathyroidal T cells in Graves' disease display restriction in V alpha T cell receptor (TcR) gene family usage, although this is not found with TcR V beta gene families in the same individuals. We have performed a qualitative analysis of TcR V alpha family usage in 12 patients with Graves' disease by reverse transcription and polymerase chain reaction (PCR) amplification of RNA extracted from isolated, unstimulated intrathyroidal lymphocytes and from snap-frozen whole thyroid specimens. No restriction was observed, with 10-15 V alpha gene families being amplified in all cases. The pattern of usage was similar to that in peripheral blood lymphocytes derived from normal subjects (n = 3) and from patients with Graves' disease (n = 3), as well as that present in the thyroids of patients with non-autoimmune toxic multinodular goitre (n = 4). These results indicated that there is no marked restriction of the unselected intrathyroidal T cell population in patients with Graves' disease who have been treated with antithyroid drugs.