Limited response to idiotype vaccination in patients with myeloma suggests that there is a need to develop better immunotherapy strategies. It has been determined that the number of high-potency CMRF44 ؉ CD14 ؊ CD19 ؊ dendritic cells (DCs) in the blood of patients with myeloma (range, 0.03%-0.8% of mononuclear cells [MNCs]; n ‫؍‬ 26) was not significantly different from that in controls (range, 0.05%-0.8% of MNCs; n ‫؍‬ 13). Expression of the costimulatory molecules CD80 and CD86 on DCs from these patients (mean, 29%؎17% of MNCs and 85%؎10% of MNCs, respectively) was also normal (mean, 29%؎17% and 86%؎16% of MNCs, respectively). Up-regulation of CD80 expression in response to stimulation by human (hu)CD40LT ؉ interleukin (IL)-2 was significantly reduced on the DCs of patients with myeloma during stable disease (n ‫؍‬ 9) and was absent during progressive stages (n ‫؍‬ 7) of disease. Similar effects were seen on B cells but not on monocytes of the same group of patients. CD86 expression on DCs was high before (86%) and after (89%)

For patients with multiple myeloma the most important laboratory correlate of prognosis and disease activity is the bromodeoxyuridine (BrdUrd) plasma cell labelling index (LI). However, the traditional immunofluorescent microscope LI technique, like other manual enumeration assays, can suffer from poor precision and accuracy. In this study the LI of different subpopulations of plasma cells (CD38++) as determined by flow cytometry was correlated with disease state. The mean LI of the total CD38++ population was significantly higher (2.7 +/- 0.4%) than the LI determined by the traditional slide technique (0.6 +/- 0.1%) for 65 samples tested. Primitive plasma cells (CD38++, CD45++) had a higher labelling index than mature plasma cells (CD38++, CD45-) (7.0 +/- 1.3% v 1.8% +/- 0.3%) and in one patient the LI of the primitive plasma cells was 46%. In addition, the LI of the mature plasma cells was lower than the total plasma cell population. As expected, there was a significant difference between the LI of patients in plateau phase and progressive disease but this difference was greatest when the LI of the primitive plasma cells was studied (9.2 +/- 2.9% v 2.2 +/- 0.7%; z = 19.9, P < 0.001). This study has raised some concerns about the sensitivity and accuracy of the traditional labelling index and has shown that the increased LI associated with progressive disease is almost entirely attributable to an increase in the LI of the primitive plasma cell subpopulation and that the LI of primitive plasma cells provides a more clinically significant correlation with disease status than the traditional assay.

Summary. The presence of T-cell clones in peripheral blood has been previously shown to be associated with a survival advantage in patients with multiple myeloma and suggests that the expanded T-cell populations may be involved in an anti-tumour response. We studied the T-cell receptor (TCR) repertoire of 38 patients with myeloma to identify and characterize the expanded T-cell populations by flow cytometry. T-cell expansions were found in 79% of the patients. The expansions occurred randomly among the 21 variable regions of the TCR b chain (Vb) studied, representing 62% of the V-b repertoire, and were stable during an 18-month follow-up. The phenotype of the expanded V-b populations was predominantly CD8 1 , CD57 1 , CD28 2 and perforin 1 , which differed significantly from the other nonexpanded Vb populations. The expression of the apoptosis markers Fas (CD95) and bcl-2 were similar between the expanded and non-expanded Vb populations. In conclusion, expanded T-cell populations were frequent in patients with myeloma, they remained unchanged during follow-up and had phenotypic characteristics of cytotoxic T cells. These data add further support to the concept that the T-cell expansions may have an immunoregulatory role in myeloma.

Summary The poor response to immunotherapy in patients with multiple myeloma (MM) indicates that a better understanding of any defects in the immune response in these patients is required before effective therapeutic strategies can be developed. Recently we reported that high potency (CMRF44+) dendritic cells (DC) in the peripheral blood of patients with MM failed to significantly up‐regulate the expression of the B7 co‐stimulatory molecules, CD80 and CD86, in response to an appropriate signal from soluble trimeric human CD40 ligand. This defect was caused by transforming growth factor β1 (TGFβ1) and interleukin (IL)‐10, produced by malignant plasma cells, and the defect was neutralized in vitro with anti‐TGFβ1. As this defect could impact on immunotherapeutic strategies and may be a major cause of the failure of recent trials, it was important to identify a more clinically useful agent that could correct the defect in vivo. In this study of 59 MM patients, the relative and absolute numbers of blood DC were only significantly decreased in patients with stage III disease and CD80 up‐regulation was reduced in both stage I and stage III. It was demonstrated that both IL‐12 and interferon‐γ neutralized the failure to stimulate CD80 up‐regulation by huCD40LT in vitro. IL‐12 did not cause a change in the distribution of DC subsets that were predominantly myeloid (CD11c+ and CDw123−) suggesting that there would be a predominantly T‐helper cell type response. The addition of IL‐12 or interferon‐γ to future immunotherapy trials involving these patients should be considered.

Deficiencies in B7:CD28 costimulation are considered to be one of the major causes of the failure to generate a tumor-specific immune response. Up-regulating the expression of the B7 molecules on malignant B cells has been shown to stimulate cytotoxic T cells. Plasma cells from patients with myeloma express a tumor-specific idiotype but lack CD80 (B7-1) and have a variable expression of CD86 (B7-2). This study has identified the incidence and clinical significance of high CD86 expression on plasma cells at diagnosis and studied the ability of trimeric human CD40 ligand (huCD40LT) to up-regulate the expression of the B7 family on malignant plasma cells. CD86 expression on plasma cells was increased in 54% of the patients studied at diagnosis (n = 35) and was associated with a significantly shorter survival (median, 28 versus 57 months; χ2 = 4.6;P = .03) and a higher tumor load (patients with more than 50% bone marrow plasma cells, 47% versus 6%; χ2 = 7.2; P = .005). CD86 expression was highest on immature and primitive plasma cells (CD38++, CD45+) of both patients and controls and was associated with a CD40+, CD20+, CD19−, CD138+ phenotype. The shortened survival was associated with high CD86 only on mature (CD38++, CD45−) plasma cells (χ2 = 7.6; P = .006). There was no significant correlation between high CD86 and other known prognostic markers, including serum β2-microglobulin, serum thymidine kinase, and labeling index. The addition of huCD40LT to short-term cultures up-regulated both CD80 and CD86 expression on B cells (CD19+) and CD80 on plasma cells (CD38++), but did not up-regulate CD86 expression on plasma cells. Thus, B7-2–positive myeloma consists of a subgroup of patients with a relatively poor prognosis, and CD40LT may be useful in immunotherapy protocols because it up-regulates CD80 expression on malignant plasma cells without inducing B7-2–positive myeloma.