Absence of high-affinity binding sites for interferon alpha/beta in variant murine CD4+ T lymphocytes not expressing the T cell antigen receptor.

The T cell antigen receptor complex (CD3/Ti) plays a role in specific antigen recognition as well as in signal transduction, with its surface expression required for the function of several other structurally distinct receptor systems, including CD2, Ly-6(TAP), and Thy-1. In this communication, evidence is presented suggesting an association between the surface expression of CD3/Ti and that of the type 1 interferon (IFN) receptor in a CD4+ murine T cell clone. We tested the proliferative responses and their capacity to be inhibited by type 1 IFN with the wild-type, CD3/Ti-positive T cell clone and its CD3/Ti-negative variants did not respond to specific antigen or anti-CD3 antibody stimulation but they did respond to T cell growth factor (TCGF), stimulation as did the wild-type parental cells. Therefore, the type 1 IFN inhibition of TCGF-stimulated proliferative responses of wild-type and variant cells were compared. Both natural and recombinant type 1 IFNs inhibited TCGF-induced tritiated thymidine (3H-TdR) incorporation in the wild-type T cell clone, with a ID50 of 60-80 U/ml. By contrast, the variants required much higher doses of type 1 IFN. The ID50 with natural murine IFN-beta was 10,000 U/ml, but this same dose of human IFN-alpha A/D gave only a marginal inhibitory effect. Accompanying the loss of IFN responsiveness, these variants also exhibited a loss of high-affinity type 1 IFN receptors. Taken together, these data suggest that the CD3/Ti complex plays a role in the surface expression of the type 1 IFN receptor in a CD4+ T cell clone.(ABSTRACT TRUNCATED AT 250 WORDS)

Adherence-mediated T cell activation in multiple sclerosis and other neurological disorders.

Peripheral blood T cells were isolated from chronic progressive multiple sclerosis patients using a stepwise protocol of density gradient centrifugation, erythrocyte rosetting and adherent cell depletion, after which T cells were cultured with no added stimulus. These cultures exhibited as much as 10-fold higher 'background' proliferative activity (designated hyperactivity) than similarly prepared cultures from normal healthy control individuals. Hyperactivity was also found with T cell cultures from patients with other neurological disorders, i.e. namely, Guillain-Barré syndrome, acute stroke, myasthenia gravis or seizures. Characterizing the hyperactivity, kinetic studies showed that it was not evident until 6 days and became maximal in 8-10 day cultures; it occurred concomitantly with an increase in activated cells; and it was inhibited by anti-HLA-DR antibody, implicating the role of CD4+ T cells. Taken together, these results suggest that the hyperactivity was the result of in vitro stimulation. In further support of this view, hyperactivity was dependent on the adherence step used in the T cell isolation procedure. Although the T cell stimulus and the mechanism underlying the adherence effect is currently speculative, the hyperactivity appears to be the result of a feature common to the diseases in which it was found. The possible roles of inflammatory events in vivo and an autologous mixed lymphocyte response in vitro are discussed.

Characterization of the binding of radioiodinated hybrid recombinant IFN-alpha A/D to murine and human lymphoid cell lines.

The hybrid recombinant human interferon (IFN) rIFN-alpha A/D was radioiodinated. Specific binding of [125I]rIFN-alpha A/D was observed with both human and murine cell lines. The binding of [125I]rIFN-alpha A/D to human Daudi cells had similar characteristics to the previously described binding of [125I]rIFN-alpha A or -alpha 2. The following lines of evidence demonstrated that [125I]rIFN-alpha A/D bound with high affinity to the same receptor on murine cells as murine IFN-alpha and -beta: (i) the binding of [125I]rIFN-alpha A/D to murine LBRM cells was inhibited to a similar extent by natural murine IFN-alpha, natural murine IFN-beta, and rIFN-A/D; (ii) the Kd (approximately 2 X 10(-10) M) obtained from both competition experiments and saturation binding experiments with [125I]rIFN-alpha A/D was comparable to the previously reported Kd for the binding of natural murine IFN-alpha and -beta to other murine cell lines; (iii) the size of the cross-linked [125I]rIFN-alpha A/D receptor complex formed on murine LBRM cells was similar to the previously reported cross-linked complex formed after binding radioiodinated natural murine IFN-beta to other murine cell lines. Due to the current lack of readily available recombinant murine IFN-alpha or -beta for radiolabeling and the previously demonstrated biological activity of rIFN-alpha A/D on murine cells, [125I]rIFN-alpha A/D should prove to be a useful reagent for further studies of murine IFN receptors.

Leukocytes from multiple sclerosis patients respond to alpha- and gamma-interferons.

Blood mononuclear leukocytes from multiple sclerosis (MS) patients were evaluated for reactivity to alpha- or gamma-interferon (IFN), using a response whereby IFN-treated (primed) cells synthesize higher levels of IFN than untreated cells. Leukocytes were treated in vitro with natural alpha-IFN, recombinant alpha-IFN, recombinant gamma-IFN, or no IFN, then exposed to measles virus to induce IFN synthesis. With no IFN treatment, IFN production by cells from the MS patients was significantly less than normal (P less than or equal to 0.025). However, with IFN treatment, cells from MS patients were primed as well as cells from normal controls: IFN synthesis for the MS patients' cells was increased 10-11-fold with either alpha-IFN preparation and 3.6-fold with gamma-IFN. These findings verify the presence of leukocyte reactivity to alpha-IFN and provide the first demonstration of responsiveness to gamma-IFN in MS.

Systemic alpha-interferon therapy of multiple sclerosis.

A randomized, double-blind, placebo-controlled crossover study tested the efficacy of natural alpha interferon in altering exacerbating-remitting MS. Twenty-four patients with frequent exacerbations were treated for 6-month periods, beginning with either 5 X 10(6) IU of interferon daily or placebo. A 6-month washout period followed each treatment. Exacerbation rates were reduced during interferon and placebo phases compared with pre-study rates; a greater reduction occurred on interferon, particularly following placebo, possibly reflecting a learning phenomenon. Fifteen patients with a strictly exacerbating-remitting course had fewer and milder exacerbations on interferon compared with those on placebo, whereas 9 patients with a progressive component continued to have active disease. These results suggest that interferon might reduce exacerbations in certain patients and indicate guidelines for future trials of interferon in MS.

Decreased interferon synthesis and responsiveness to interferon by leukocytes from multiple sclerosis patients given natural alpha interferon.

Despite the use of interferon (IFN) in numerous clinical trials, relatively little is known about how IFN therapy influences leukocyte function. To evaluate some of its effects, leukocytes from multiple sclerosis (MS) patients given daily treatments of natural alpha IFN (IFN-alpha) were evaluated for IFN synthesis and two responses to IFN in vitro: enhancement (priming) of IFN synthesis and suppression of Concanavalin A (Con A)-induced T-cell mitogenesis. The IFN therapy had no effect on the sensitivity of Con A-stimulated leukocytes to the antiproliferative action of IFN-alpha. However, using Newcastle disease virus (NDV), measles virus, or poly I:C to stimulate IFN synthesis, cells from IFN-treated patients produced less IFN in response to all inducers, with titers ranging between 11% and 44% of pretherapy values. Also, unlike cells from these same patients before therapy or from the placebo recipients, cells from the IFN recipients were not primed by either IFN-alpha or -beta even though IFN-beta had not been used for therapy. The loss of these priming reactivities suggests that resistance to IFN had developed in IFN-treated patients.