SummaryOlder people suffer from a decline in immune system, which affects their ability to respond to infections and to raise efficient responses to vaccines. Effective and specific antibodies in responses from older individuals are decreased in favour of non-specific antibody production. We investigated the B-cell repertoire in DNA samples from peripheral blood of individuals aged 86-94 years, and a control group aged 19 -54 years, using spectratype analysis of the IGHV complementarity determining region (CDR)3. We found that a proportion of older individuals had a dramatic collapse in their B-cell repertoire diversity. Sequencing of polymerase chain reaction products from a selection of samples indicated that this loss of diversity was characterized by clonal expansions of B cells in vivo.Statistical analysis of the spectratypes enabled objective comparisons and showed that loss of diversity correlated very strongly with the general health status of the individuals; a distorted spectratype can be used to predict frailty. Correlations with survival and vitamin B12 status were also seen. We conclude that B-cell diversity can decrease dramatically with age and may have important implications for the immune health of older people. B-cell immune frailty is also a marker of general frailty.

As with BMD, alendronate impairs the action of teriparatide to increase bone turnover in men.

Young patients with myasthenia gravis (MG) frequently have ectopic GC in their thymus. We investigated these ectopic GC by microdissection of GC B cells and analysis of their Ig gene characteristics, in comparison to normal GC. CDR3 length distribution, a measure of clonal variability, and Ig gene family usage were similar in MG and normal tonsil samples. Lineage tree analysis demonstrated similar diversification and mutations per cell compared with normal control trees. Mutations were observed in the framework regions, responsible for the structural integrity of the BCR; however, these mutations were mostly conservative or neutral, confirming that a functional BCR is conserved in MG. In the CDR, responsible for Ag binding, selection against replacement mutations was revealed. This may indicate that the MG clones analyzed are already highly Ag-specific, and therefore potential affinity-reducing replacement mutations in the CDR3 are not propagated, due to Ag-driven selection. Somatic hypermutation (SHM) targeting motifs and aa substitution preferences in MG were similar to those of normal controls. Overall, these results suggest that B cells in the ectopic GC in MG appear to undergo normal diversification and selection, in spite of the chronic nature and different environment of the response.Key words: GC . Ig . myasthenia gravis . Somatic hypermutation . Thymus IntroductionMyasthenia gravis (MG) is an autoimmune condition characterized by muscle weakness, which fluctuates over time. Transmission at the neuromuscular junction is impaired due to autoantibodies (autoAb), which bind to the nicotinic acetylcholine receptors (AChR) in 80-85% of patients and, to musclespecific tyrosine kinase in about 5% of patients [1].Studies so far have focused on pro-inflammatory cytokines, which were shown to induce increased thymic expression of the auto-Ag AChR and presentation to autoreactive T cells [2]. However, emerging data have renewed interest in the importance of B cells in the pathophysiology of neurological autoimmune disorders, such as MG. The establishment of a large B-cell compartment in the thymus of MG patients may be partly attributable to the observed increase in the expression of APRIL and BAFF, which are known B-cell survival enhancing factors [3].The generation of high-affinity AChR autoAb requires activated CD41 T cells to interact with B cells resulting in hypermutation of initially low-affinity anti-AChR Ab [1]. AChR-specific CD4 1 T cells are present in both the blood and the thymus of MG Ã These authors contributed equally to this work. patients. The Ab response is polyclonal and predominantly composed of different IgG subclasses [4]. Though the presence of AChR autoAb is indicative of MG, the titer does not always correspond to severity [4]. It has been observed that patients seronegative for AChR autoAb may in fact possess thymic B cells that do secrete AChR autoAb [5]. These are sometimes low-affinity AChR autoAb which cannot always be detected in solution-phase assays, but can be detected using more...

There is very little change in the quantity of antibodies people produce, of any isotype, with age. However, there is a change in the quality of the antibody response. Older people produce fewer antibodies that are specific for the activating pathogen or vaccine. At the same time, the number of nonspecific antibodies increases. Quite often these antibodies have self-reactivity (e.g., anti-dsDNA). The appearance of these antibodies is not associated with pathogenic autoimmune disease, although it is true that the incidence of some autoimmune diseases increases with age. The authors postulate that the process of antibody affinity maturation is compromised in old age. No evidence was found that the process of hypermutation is compromised with age. However, using graph theory to study the dynamics of a germinal center selection process, a decrease in the extent of selection occurring in the germinal centers of mucosal tissue was observed with age. This is a tissue-specific phenomenon because the decrease was not seen in the germinal centers of spleen. Because selection of highly specific cells in the germinal center depends on a number of factors (number and quality of founder cells, help from T cells, and follicular dendritic cells) these need to be investigated further to determine what is needed to improve the affinity mutation process.

Immunisation of certain rodent strains, of particular MHC types with heterologous type I1 collagen (CII) results in the development of an acute arthritic disease called collagen-induced arthritis (CIA) [l]. The disease is thought to result from anticollagen antibody immune complex-mediated development of synovitis and macrophage-mediated erosive cartilage destruction. The disease has also been shown to be T cell dependent since T cell depleted animals are not susceptible to arthritis [2] and the disease can be successfully treated with anti-CD4 [3] and anti-TCR monoclonal antibodies [4]. Significantly, T cell proliferative responses have been shown to immunodominant epitopes of CII, located particularly in the cyanogen bromide (CB) fragment CB 1 1 [5,6]. Intradennal immunisation of Lewis rats (MHC RT1-1) with bovine CII (KII) leads to an acute inflammatory response from day 14 post immunisation. In order to determine the phenotype and functional properties of T cells reactive with epitopes of CII implicated in the pathology and regulation of CIA, the generation of CII specific T cell lines and clones in Lewis rats was embarked upon.Draining lymph node cells (LNC) from bCII immunised rats were harvested at day 14 and set up in bulk culture with bCII (2Opglml) in RPMI supplemented with 2% normal rat serum. At day 4 massive proliferative responses (CPM=90,358) of whole LNCs in the presence of bCII were observed (SI=26). Characterisation of these responding cells by FACscan analysis showed an expanding population of CD4+. MHC II+, IL-2 receptor+ and CD45RC-T cells. In order to determine suitable antigen presenting cells ( A X ) for presentation of bCII at restimulation a proliferation assay was also set up with separated T cells and different sources of Apc. T cell proliferation and SI was greatest with a ratio of 1 T cell : 20 thymocytes, normal LNC gave a poor SI and splenocytes were found to be inhibitory. At day 12 of bulk culture, when the cells were rested, viable cells were harvested and restimulated with thymocytes pulsed overnight with or without bCII. Following restimulation a large proliferative response to the addition of thymocytes alone was observed within 24 hours, peaking at 48 hours (Fig. 1). . . Fig. 1 u s AFC is Responder cells were harvested from bCII stimulated cultures at day 12 and restimulated with bCII-pulsed or non-pulsed, mitomycin-C treated thymocytes. Responder cells were used at 5x104/well and were plated out in triplicate. Tritiated thymidine was added for the final 6 hours of culture and the assay was harvested at 48 hours.Abbreviations used CIA-collagen-induced arthritis, CII-type I1 collagen, LCII-bovine type I1 collagen, LNC-lymph node cell, APC-antigen presenting cell, OVA-ovalbumin.This autoreactive response increased with increasing numbers of thymocytes added and was also seen with splenocytes and normal LNCs as AFC. Numerous changes to the protocol e.g. the omission of IL-2 to reduce bystander expansion in order to try and generate CII specificity were unsuccessful; autoreactiv...