Sex-related immune changes in young mice

Here we describe changes in selected immune parameters related to age and sex in young mice. We focused on the T cell compartment and studied thymuses and spleens from mice 3 to 9 weeks of age in order to bracket the time period around murine puberty. With regard to distribution of immune cells, no significant sex-related changes were seen in thymocyte expression of CD3, CD4, CD8, or CD4/CD8 or splenocyte expression of CD3, CD4, CD8, or CD45R/B220, a pan B cell marker. For splenocytes, significantly more cells were positive for CD3 in older (6-9 week old) compared with younger (3-4 week old) mice. Splenocyte and thymocyte cell proliferation as measured by DNA synthesis in response to in vitro mitogens was compared for cells from male and female mice over the ages studied. Thymocyte proliferation was not related to age or sex of the mice. For splenocytes of the youngest mice (3 weeks old), the response to a cell surface-receptor-independent mitogenic combination of phorbol ester and ionomycin induced a significantly greater response in cells from female mice compared with male mice. This trend was reversed for mice of 4-6 weeks of age, where the response by splenocytes from males was significantly greater than that by cells from females. For mice 7-8 weeks of age, splenocytes from female mice responded significantly less to stimulation by antibody to CD3, a component of the T-cell receptor. Our results demonstrate that depending on the assays employed, sexual dimorphism in the immune system may be demonstrated prior to puberty.

Onchocerca volvulus: identification and characterization of an immunogenic eggshell protein (Oveg1)

A major antigen recognized by human sera in Onchocerca volvulus infections is a parasite eggshell protein. The cDNA clone for this antigen was isolated from a lambda gt11 O. volvulus cDNA library using antisera from patients with high microfilarial counts. Sequence analysis of the cDNA clone predicts a polyglutamine repeat near the 5' end of the cDNA, and a motif of four arginines near the 3' end, reminiscent of that found in many regulatory proteins. The cDNA was subcloned into a yeast expression vector and reagent quantities of recombinant antigen produced in Saccharomyces cerevisiae. Antisera produced to the recombinant purified protein localized the antigen to the eggshell of developing microfilariae within the adult female uterus. No other sites of Oveg1 expression were noted in adult worms, but labeling was seen in internal membrane structures of L3 larvae. Sera from infected chimps recognized Oveg1 only after infections became patent. Sera from infected humans showed reactivity to Oveg1 that varied from 39 to 95%, depending upon the geographic location.

Levamisole meets sulfhydryl requirements of CTLL-2 cells and mediates enhanced proliferative response to mitogen stimulation without increasing interleukin-2 production

We examined the effect of levamisole (LMS) on the proliferative response and interleukin-2 (IL-2) concentration in OKT3-, phytohemagglutinin-, and concanavalin-A-stimulated lymphocyte cultures. Although proliferative response was enhanced in lymphocyte cultures stimulated in the presence of LMS, similar levels of IL-2 were observed in stimulated and unstimulated cultures. The mechanism of the enhancement effect of LMS on proliferative response was further characterized by studying its effects on the growth of IL-2-dependent CTLL-2 cells in culture. Since this cell line has been shown to require 2-mercaptoethanol (2-ME) for normal growth in recombinant IL-2, the effect of LMS on several parameters of its growth was compared with that of 2-ME. Unlike 2-ME, LMS did not enhance 35S-cystine uptake. Both compounds increased thiol concentration in the cell culture, but (oxidized) 2-ME induced a greater increase. Generally, the effects of LMS on CTLL-2 growth were quite similar to those of structurally unrelated compounds known to have antioxidant properties, and the demonstrated thiol requirement of this cell line for growth in recombinant IL-2 was met by substituting LMS for 2-ME. When the effect of LMS on IL-2 receptor (IL-2R) expression in CTLL-2 cells was examined by a receptor-ligand binding assay involving low levels (10-80 pM) of 125IL-2, a modest increase in the level of IL-2R expression was observed. The biologically active high-affinity IL-2R complex is believed to be preferentially bound at the low levels of 125IL-2 used here, suggesting a functional relevance for this effect of LMS. These observations should be useful in minimizing the cost and duration of in vitro expansion of lymphocytes for use in adoptive immunotherapy and should be applicable in improving the response of immunologically impaired patients to immunotherapy.

Patterns of cytokines released by peripheral blood leukocytes of normal donors and cancer patients during interleukin-2 activation in vitro

We have examined the responsiveness to in vitro stimulation with high-dose recombinant interleukin-2 (IL-2) of peripheral blood leukocytes (PBLs), collected from normal donors, or from successive daily cytaphereses of cancer patients with a range of advanced malignancies, following 5 days of continuous infusion with IL-2 in vivo. Normal donor PBLs showed a transient release of tumor necrosis factor (TNF) (up to 400 pg/ml) during the first day, while factors including interferon-gamma (IFN-gamma), soluble IL-2 receptor, and soluble CD-8 showed a gradual increase to modest levels (at best) during the 4 day incubation with IL-2. In contrast, the cancer patients' PBLs, after 5 days of IL-2 activation in vivo, responded with one of two patterns of production of cytokines. In pattern I, exposure to the IL-2 resulted in a transient release of TNF during the first 48 h. The level of TNF released showed a progressive increase from PBLs harvested from the first cytapheresis (up to 50 pg of TNF/ml) through the fourth cytapheresis (up to 2,000 pg of TNF/ml). Additionally, pattern I PBLs showed significant levels of production of IFN-gamma, soluble IL-2 receptor, and soluble CD8. In pattern II, the patients' PBLs from each cytapheresis released only low levels of TNF (less than 300 pg/ml) and minimal levels of IFN-gamma, IL-2 receptor, and CD8. A pattern I response is considered to be consistent with an immunostimulatory role for IL-2, which induces a cooperative interaction of lymphocytes and macrophages that is mediated by other cytokines, while pattern II may reflect an immunosuppression in these patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Extracellular proteases of Onchocerca

Two important events in infection by Onchocerca parasites involve cutaneous tissue migration by larval stages. L3 larvae migrate from the blackfly bite site to subcutaneous locations for adult development, and microfilariae from subcutaneous nodules to distant regions of the skin and sometimes the eye. By analogy to other tissue-invasive helminth larvae, it has been proposed that migration of Onchocerca larvae through cutaneous tissue is facilitated by secretion of proteolytic enzymes. To test this hypothesis, neutral protease activity capable of degrading a model of cutaneous extracellular matrix was assayed using live L3 larvae of O. lienalis and microfilariae of O. cervicalis and O. cervipedis. Five hundred L3 larvae degraded most of the matrix within 24 hr of incubation. Substrate gel electrophoresis and other protease assays showed a 43-kDa serine elastase was secreted by O. lienalis L3 larvae. Larvae and adults of the free-living nematode, Caenorhobditis elegans, by contrast, did not secrete neutral proteases and large numbers of motile C. elegans juveniles and adults produced no degradation of the extracellular matrix. Expression of Onchocerca neutral protease activity was stage specific. No protease activity corresponding to that seen in L3 larvae was found in adult worms. Microfilariae of O. cervicalis and O. cervipedis produced both a serine and a metalloprotease, but the level of protease activity of these microfilariae was substantially lower than that of L3 larvae, and no significant protease activity was detected in extracts of O. lienalis microfilariae. Uterine microfilariae of O. cervicalis had different protease species than skin microfilariae, suggesting that changes in protease expression parallel other morphologic and biochemical changes in the development of skin microfilariae. The serine protease of L3 larvae probably plays an important parasitic function, facilitating L3 migration from the blackfly bite site to distant regions of the body where adults will develop and form nodules. The protease activity of microfilariae, while individually considerably less than that of L3 larvae, may still contribute to the tissue destruction seen with heavy skin densities of microfilariae.

The 46-kDa nucleoside triphosphatase of rat liver nuclear scaffold represents the N-terminal portion of lamins A/C

The major nucleoside triphosphatase (NTPase) of rat liver nuclear scaffold (NS) or envelope, which is thought to participate in nucleocytoplasmic transport, has been identified via photoaffinity labeling as a 46-kDa polypeptide. This 46-kDa protein was purified by SDS-polyacrylamide gel electrophoresis and cleaved with trypsin. The resulting peptides were purified by HPLC and five were microsequenced. All five peptides appear to be derived from the N-terminal region of lamins A/C. Subsequent experiments with photolabeled NS showed that the 46-kDa polypeptide was selectively immunoprecipitated by antiserum specific to lamins A/C and by affinity-purified anti-lamin antibodies. Photolabeling of nuclei prepared in the presence of protease inhibitors showed predominant labeling of the 46-kDa polypeptide, suggesting that it is an integral nuclear constituent and not an artifact produced during NS preparation. Use of protease inhibitors throughout purification of NS increased the specificity of photolabeling of the 46-kDa band by significantly reducing photolabeling of smaller molecular weight components, which arise by proteolysis. Anti-lamin antibodies also produced a significant inhibition of NTPase activity in NS. These results suggest that the N-terminal portion of lamins A/C represents the 46-kDa NTPase, which, according to previous reports, may participate in RNA transport.

Cloning of rat "prion-related protein" cDNA

Rat prion-related protein (PrP) cDNA has been cloned and sequenced. Comparison of this cDNA with those from human, hamster, and mouse indicates extremely high conservation (about 95%). The deduced partial rat PrP possesses: (a) a highly conserved region composed of repetitive sequences in what is presumably an extracellular domain, (b) a hydrophobic transmembrane domain, (c) a highly charged region which should stop membrane transfer, (d) a substantial cytoplasmic domain (which contains all of the nonconservative substitutions and a high proportion of conservative substitutions), and (e) a hydrophobic C-terminus. Dot and Northern blot analyses suggest a limited expression of PrP in rat tissues and indicate that PrP expression is decreased in the brain during the acute phase response systemically. Our results lend support to the notion that PrP is a highly conserved, normal cellular membrane protein of essential (although unknown) biologic function, which may be deposited in fibrillar amyloid form as a result of abnormal processing.

Apparent interleukin 2 (IL-2) inhibitory activity of human serum is due to rapid killing of IL-2-dependent mouse cells

A number of investigators have reported that human serum inhibits the proliferation of IL-2-dependent mouse cells in IL-2 bioassays, but the mechanism of inhibition has not been carefully examined. We noticed that IL-2-dependent mouse cells (CTLL-2) are killed within 30 min in the presence of a 1/10 dilution of human serum. However, CTLL-2 cells totally deprived of IL-2 did not begin to die until at least 6 h in culture. Thus, even complete inhibition of IL-2 by human serum could not account for the rapid cytotoxicity caused by human serum. Since humans have 'natural' antibodies which react with mouse cells, it seemed possible that the cytotoxicity was due to antibody/complement-mediated cell lysis. This was supported by the observation that EDTA (at a concentration sufficient to inhibit complement) protected CTLL-2 cells from the cytotoxic effects of human sera from four normal donors. In addition, preincubation of CTLL-2 cells with heat-inactivated human sera at 4 degrees C rendered them much more susceptible to lysis with rabbit complement than cells which were preincubated with complete culture medium. The cytotoxicity of human serum is not limited to IL-2-dependent mouse cells but was also observed with EL4 and Ag8.653 cells as well as normal splenocytes. The cytotoxic effect of human serum was lost upon removal of IgM, but not upon removal of IgG. These results strongly suggest that the inhibition of proliferation of IL-2-dependent mouse cells by human serum is due to antibody/complement-mediated lysis of those cells. In addition, non-heat-inactivated human serum did not inhibit the IL-2-mediated proliferation of human PHA blasts, indicating that there is no inherent inhibitory activity in human serum apart from the cytotoxic effect on xenogeneic cells. Thus the reported IL-2 inhibitory activity of whole human serum is probably not biologically relevant.

Purification of prealbumin from human serum

A method is presented by which prealbumin (thyroxine-binding prealbumin; tryptophan-rich prealbumin) may be purified to homogeneity from human serum. The method involves precipitation of contaminating proteins with dilute aqueous phenol, ion-exchange chromatography on DEAE-Sephacel, and gel permeation chromatography on Sephadex G-100. The yield is 25-30%, and the prealbumin is homogeneous by polyacrylamide gel electrophoresis at pH 8.9 and pH 3.6.

Suppression of interleukin 2 activity by natural products: effects of serum lipoproteins

The results presented here demonstrate that mouse serum lipoproteins inhibit Interleukin 2 (IL2)-mediated proliferation of CTLL-2 cells. Lipoproteins account for a variable portion (29-83%) of the total inhibitory activity of whole serum and are not specific inhibitors of IL2-mediated cell proliferation, as evidenced by their inhibitory activity for non-IL2-dependent MPC 11 cells. Lipoproteins did not accelerate the death of CTLL-2 cells deprived of IL2, indicating that their inhibition of proliferation is not due to toxic effects. Finally, the inhibitory activity of serum and isolated lipoproteins was increased when the donor mice were maintained on a diet high in polyunsaturated fats for 16 days prior to bleeding. These findings provide a basis for future investigations of the relationship between dietary fats, lipoprotein quantity and composition, and alteration of immune responses.

The major nucleoside triphosphatase of nuclear scaffold is distinct from actin

The major nucleoside triphosphatase of rat liver nuclear scaffold, a 46 kD protein thought to participate in nucleocytoplasmic RNA translocation, is distinct from immunologically-identified scaffold actin on Western blots, has a substantially different amino acid composition, and its enzymatic activity is not affected by anti-actin antibodies. Thus, although the contractile protein actin is found in nuclear scaffold and appears to interact with RNA, it is not associated with the nucleoside triphosphatase activity in such preparations.

A quantitative, non-isotopic bioassay for interleukin 2

A quantitative bioassay for IL2 is described in which an electronic particle counter is used to measure IL2-mediated proliferation of an IL2-dependent cell line. The assay requires no radioisotopes, is comparable to tritiated thymidine incorporation and can be completely performed in about 28 hours. It can also be used to measure inhibition of IL2-mediated proliferation.