Chronic lymphocytic leukemia cells diversify and differentiate in vivo via a nonclassical Th1-dependent, Bcl-6-deficient process.

Xenografting primary tumor cells allows modeling of the heterogeneous natures of malignant diseases and the influences of the tissue microenvironment. Here, we demonstrate that xenografting primary chronic lymphocytic leukemia (CLL) B lymphocytes with activated autologous T cells into alymphoid mice results in considerable CLL B cell division and sizable T cell expansion. Nevertheless, most/all CD5+CD19+ cells are eventually lost, due in part to differentiation into antibody-secreting plasmablasts/plasma cells. CLL B cell differentiation is associated with isotype class switching and development of new IGHV-D-J mutations and occurs via an activation-induced deaminase-dependent pathway that upregulates IRF4 and Blimp-1 without appreciable levels of the expected Bcl-6. These processes were induced in IGHV-unmutated and IGHV-mutated clones by Th1-polarized T-bet+ T cells, not classical T follicular helper (Tfh) cells. Thus, the block in B cell maturation, defects in T cell action, and absence of antigen-receptor diversification, which are often cardinal characteristics of CLL, are not inherent but imposed by external signals and the microenvironment. Although these activities are not dominant features in human CLL, each occurs in tissue proliferation centers where the mechanisms responsible for clonal evolution operate. Thus, in this setting, CLL B cell diversification and differentiation develop by a nonclassical germinal center-like reaction that might reflect the cell of origin of this leukemia.

Serum LAIR-2 is increased in autoimmune thyroid diseases.

Leukocyte-associated Ig-like receptor (LAIR) is a small family-receptor able to inhibit immune cell function via collagen binding. It exists as both membrane-bound and soluble forms. LAIR-1 functions as an inhibitory receptor on natural killer cells, T lymphocytes and monocytes. In addition to LAIR-1, the human genome encodes LAIR-2, a soluble homolog. Several studies have focused on LAIR-1, whereas few investigations concentrate on the expression and function of LAIR-2. We demonstrate the presence of high LAIR-2 levels in 74/80 sera from patients with autoimmune thyroid diseases (both Graves' disease and autoimmune thyroiditis). LAIR-2 levels seemed not to be related to specific clinical manifestations, such as thyroid functions (hypo- or hyperthyroidism), or specific clinical features (such as ophtalmopathy). In addition, serum LAIR-2 is able, in vitro, to bind its natural ligand, collagen. Since LAIR-2 has been found to have higher affinity for collagens than LAIR-1 did, we hypothesize a potential regulating capability of serum LAIR-2 in finally regulating the inhibitory capability of LAIR-1.

A soluble form of CTLA-4 is present in paediatric patients with acute lymphoblastic leukaemia and correlates with CD1d+ expression.

CTLA-4 is a key factor in regulating and maintaining self tolerance, providing a negative signal to the T cell and thus limiting immune responses. Several polymorphisms within the CTLA-4 gene have been associated with an increased risk of developing autoimmune diseases and, very recently, with susceptibility to human cancer. Acute lymphoblastic leukemia is a clonal disorder of lymphoid progenitors representing the most frequent malignancy of childhood. Here, we show the presence at significantly elevated levels of a circulating soluble form of CTLA-4 in 70% of B-ALL pediatric patients with active disease, the positive correlation between the percentage of leukemic B lymphocytes and the amount of serum sCTLA-4, and the expression of sCTLA-4 transcript by B cells in patients. Finally, a correlation between CD1d expression (a negative prognostic marker) and the sCTLA-4 in B-ALL patients was observed. This suggests a possible role of this soluble molecule as a marker of progression or severity of the neoplastic disease.

A novel adoptive transfer model of chronic lymphocytic leukemia suggests a key role for T lymphocytes in the disease.

Chronic lymphocytic leukemia (CLL) is an incurable adult disease of unknown etiology. Understanding the biology of CLL cells, particularly cell maturation and growth in vivo, has been impeded by lack of a reproducible adoptive transfer model. We report a simple, reproducible system in which primary CLL cells proliferate in nonobese diabetes/severe combined immunodeficiency/γc(null) mice under the influence of activated CLL-derived T lymphocytes. By co-transferring autologous T lymphocytes, activated in vivo by alloantigens, the survival and growth of primary CFSE-labeled CLL cells in vivo is achieved and quantified. Using this approach, we have identified key roles for CD4(+) T cells in CLL expansion, a direct link between CD38 expression by leukemic B cells and their activation, and support for CLL cells preferentially proliferating in secondary lymphoid tissues. The model should simplify analyzing kinetics of CLL cells in vivo, deciphering involvement of nonleukemic elements and nongenetic factors promoting CLL cell growth, identifying and characterizing potential leukemic stem cells, and permitting preclinical studies of novel therapeutics. Because autologous activated T lymphocytes are 2-edged swords, generating unwanted graph-versus-host and possibly autologous antitumor reactions, the model may also facilitate analyses of T-cell populations involved in immune surveillance relevant to hematopoietic transplantation and tumor cytoxicity.

Identification of a novel antibody associated with autoimmune pancreatitis.

BACKGROUND: Autoimmune pancreatitis is characterized by an inflammatory process that leads to organ dysfunction. The cause of the disease is unknown. Its autoimmune origin has been suggested but never proved, and little is known about the pathogenesis of this condition. METHODS: To identify pathogenetically relevant autoantigen targets, we screened a random peptide library with pooled IgG obtained from 20 patients with autoimmune pancreatitis. Peptide-specific antibodies were detected in serum specimens obtained from the patients. RESULTS: Among the detected peptides, peptide AIP(1-7) was recognized by the serum specimens from 18 of 20 patients with autoimmune pancreatitis and by serum specimens from 4 of 40 patients with pancreatic cancer, but not by serum specimens from healthy controls. The peptide showed homology with an amino acid sequence of plasminogen-binding protein (PBP) of Helicobacter pylori and with ubiquitin-protein ligase E3 component n-recognin 2 (UBR2), an enzyme highly expressed in acinar cells of the pancreas. Antibodies against the PBP peptide were detected in 19 of 20 patients with autoimmune pancreatitis (95%) and in 4 of 40 patients with pancreatic cancer (10%). Such reactivity was not detected in patients with alcohol-induced chronic pancreatitis or intraductal papillary mucinous neoplasm. The results were validated in another series of patients with autoimmune pancreatitis or pancreatic cancer: 14 of 15 patients with autoimmune pancreatitis (93%) and 1 of 70 patients with pancreatic cancer (1%) had a positive test for anti-PBP peptide antibodies. When the training and validation groups were combined, the test was positive in 33 of 35 patients with autoimmune pancreatitis (94%) and in 5 of 110 patients with pancreatic cancer (5%). CONCLUSIONS: The antibody that we identified was detected in most patients with autoimmune pancreatitis but also in some patients with pancreatic cancer, making it an imperfect test to distinguish between these two conditions.

Soluble CTLA-4 in autoimmune thyroid diseases: relationship with clinical status and possible role in the immune response dysregulation.

CTLA-4 molecule, expressed by activated T and B lymphocytes, transduces an inhibitory signal. Increasing evidence showed CTLA-4 gene as an important susceptibility locus for autoimmune endocrinopathies and other autoimmune disorders. The aim is to evaluate the augmented sCTLA-4 serum levels in different autoimmune thyroid diseases when compared with normal donors or with non-autoimmune hyperthyroidism and to investigate the functional activities and suggest the possible pathogenetic role of sCTLA-4. We demonstrate the presence of a soluble form of CTLA-4 in 59/90 sera from patients with autoimmune thyroid diseases (both Graves' disease and autoimmune thyroiditis). sCTLA-4 levels were not related to specific clinical manifestations, such as clinical thyroid status (hypo- or hyperthyroidism), circulating thyroid hormones, or other clinical features (ophthalmopathy). sCTLA-4 production does not seem to be affected by disease evolution during time. We showed that sCTLA-4 from sera of patients with thyroid autoimmunity is able to bind its physiological ligands CD80/CD86 and displays functional activities on different in vitro systems (T-cell proliferation induced by specific soluble antigens, bi-directional mixed lymphocyte reaction). In conclusion, we demonstrate an increment of sCTLA-4 in serum of patients with autoimmune thyroid diseases. Its possible pathogenetic role during autoimmune processes can be speculated: sCTLA-4 can specifically inhibit the early T-cell activation by blocking the interaction of CD80/CD86 with the co-stimulatory receptor CD28. Conversely, higher levels of sCTLA-4 could compete with membrane-bound CTLA-4 for CD80/CD86, in later T lymphocytes activation phase, causing a reduction of inhibitory signaling.