Sera of patients with rheumatoid arthritis contain antibodies to recombinant human T-lymphotrophic virus type I/II envelope glycoprotein p21

Dysfunction of immune system in the development of large granular lymphocyte leukemia

OBJECTIVES

Large granular lymphocyte (LGL) leukemia is a rare type of lymphoproliferative disease caused by clonal antigenic stimulation of T cells and natural killer (NK) cells.

METHODS

In this review, we focus on the current knowledge of the immunological dysfunctions associated with LGL leukemia and the associated disorders coexistent with this disease. Novel therapeutic options targeting known molecular mechanisms are also discussed.

RESULTS AND DISCUSSION

The pathogenesis of LGL leukemia involves the accumulation of gene mutations, dysregulated signaling pathways and immunological dysfunction. Mounting evidence indicated that dysregulated survival signaling pathways may be responsible for the immunological dysfunction in LGL leukemia including decreased numbers of neutrophils, dysregulated signal transduction of NK cells, abnormal B-cells, aberrant CD8+ T cells, as well as autoimmune and hematological abnormalities.

CONCLUSION

A better understanding of the immune dysregulation triggered by LGL leukemia will be beneficial to explore the pathogenesis and potential therapeutic targets for this disease.

The spectrum of large granular lymphocyte leukemia and Felty's syndrome

PURPOSE OF REVIEW

Patients with chronic large granular lymphocyte (LGL) leukemia often have rheumatoid arthritis (RA), neutropenia and splenomegaly, thereby resembling the manifestations observed in patients with Felty's syndrome, which is a rare complication of RA characterized by neutropenia and splenomegaly. Both entities have similar clinical and laboratory presentation, as well as a common genetic determinant, HLA-DR4, indicating they may be part of the same disease spectrum. This review paper seeks to discuss the underlying pathogenesis and therapeutic algorithm of RA, neutropenia and splenomegaly in the spectrum of LGL leukemia and Felty's syndrome.

RECENT FINDINGS

We hypothesize that there may be a common pathogenic mechanism between LGL leukemia and typical Felty's syndrome. Phenotypic and functional data have strongly suggested that CD3 LGL leukemia is antigen-activated. Aberrations in the T-cell repertoire with the emergence of oligoclonal/clonal lymphoid populations have been found to play a pivotal role in pathogenesis of RA. The biologic properties of the pivotal T cell involved in RA pathogenesis are remarkably similar to those in leukemic LGL.

SUMMARY

RA-associated T-cell LGL leukemia and articular manifestations of typical Felty's syndrome are not distinguishable. A common pathogenetic link between LGL leukemia and RA is proposed.

Characterization of HTLV envelope seroreactivity in large granular lymphocyte leukemia

T-cell large granular lymphocyte (T-LGL) leukemia is a rare chronic lymphoproliferative disorder of unknown etiology. We have previously reported that patients with T-LGL leukemia were seroreactive against BA21, a 34 amino acid peptide derived from HTLV-I envelope protein p21. We tested sera from 70 patients with T-LGL leukemia and found that 21/70 (30%) of them were seroreactive against fusion peptide GST-BA21. In control group of healthy blood donors 3/30 (10%) were seroreactive. We synthesized a set of overlapping peptides derived from BA21 and tested them against sera from patients. Only a single peptide (p21 env 417-430) showed reactivity. We then generated multiple fusion peptides consisting of 5-14 amino acid residues derived from this peptide and tested them against patient and control sera. Shortest peptide giving positive seroreactivity was octapeptide P8 (p21 env 418-425). Competitive Western blot assay with use of fusion peptides revealed that the minimal HTLV-I epitope responsible for seroreactivity found in patients with T-LGL leukemia is a decapeptide PP10 (p21 env 417-426). Protein Bank (NCBI) search did not reveal any significant homology between PP10 epitope and known human proteins. These results further define the epitope responsible for HTLV env seroreactivity observed in LGL leukemia.

Imaging Findings in Musculoskeletal Complications of AIDS

Patients with human immunodeficiency virus (HIV) infection and acquired immunodeficiency syndrome (AIDS) are susceptible to a variety of complications that can affect the musculoskeletal system. These complications can be infectious, inflammatory, or neoplastic or can take some other form. Infection (cellulitis, necrotizing fasciitis, soft-tissue abscess, pyomyositis, osteomyelitis, septic arthritis) is the most common complication. Inflammatory processes include various arthritides as well as polymyositis. Non-Hodgkin lymphoma and Kaposi sarcoma are the two most common neoplasms in this patient population. Miscellaneous disorders include osteonecrosis, osteoporosis, rhabdomyolysis, anemia-related abnormal bone marrow, and hypertrophic osteoarthropathy. The underlying mechanisms leading to these diseases are complex and not fully understood but are thought to be multifactorial. Radiology may play an important role in early diagnosis and treatment planning in this population, in whom clinical and laboratory findings are commonly equivocal and nonspecific. Although biopsy is often necessary for the final diagnosis, it is important for the radiologist to be familiar with the different types of musculoskeletal disease in HIV-positive and AIDS patients so that an appropriate differential diagnosis can be established.

Epitope mapping of HTLV envelope seroreactivity in LGL leukaemia

Sera from approximately 50% of patients with large granular lymphocyte (LGL) leukaemia react with a recombinant human T-cell leukaemia/lymphoma virus (HTLV) transmembrane envelope protein, p21e. Two immunodominant epitopes within env p21e have been defined by reactivity against recombinant proteins GD21 and BA21. In this study sera from 41 patients with LGL leukaemia were examined for reactivity against these recombinant HTLV env proteins. Overall, 21/41 (51%) sera reacted to p21e. Only two sera reacted to GD21. The predominant immunoreactivity against p21e was directed against the BA21 epitope, with 19/41 (46%) sera being BA21 positive. Seroconversion to BA21 protein was also documented. PCR analyses confirmed the low incidence of protypical HTLV sequences (2/41, 5%). These data document an association between BA21 seroreactivity and LGL leukaemia. This finding raises the possibility that such BA21 seroreactivity could be due to cross-reactivity to a cellular or retroviral antigen sharing some amino acid homology with the transmembrane glycoprotein of HTLV.

HIV infection-associated inflammatory musculoskeletal disorders

Inflammatory musculoskeletal complaints are relatively common during the course of HIV infection, although they tend to be more frequent during late stages. The clinical spectrum is varied, ranging from arthralgias to distinct rheumatic disorders, such as Reiter's syndrome and psoriatic arthritis. The therapeutic management often poses a challenge, although most patients respond to conventional first- and second-line anti-inflammatory medications.

[Pathogenesis of rheumatoid arthritis]

BACKGROUND

Despite ongoing intensive research using sophisticated new molecular tools and methods, the pathogenesis of autoimmune diseases such as rheumatoid arthritis (RA) is still not completely understood.

HYPOTHESES

In this paper the two favorite hypotheses of the pathogenesis of rheumatoid arthritis currently discussed are introduced and compared. Hypothesis 1 is focussing on the central role of the T cells and T cell dependent phenomena in the pathogenetic scenario of RA. In contrast, hypothesis 2 stresses the role of altered synovial fibroblasts and their specific features critical for the destruction of inflamed joints. Both hypotheses are thoroughly discussed and suggestions for further research activities are made.

CONCLUSION

Insights in the pathogenesis of RA provide options to develop new therapeutic strategies aimed at the inhibition of pathogenetic relevant processes.