Concanavalin A-treated Lymphocytes Research Articles

The immune-enhancing potential of peptide fractions from fermented Spirulina platensis by mixed probiotics.

Mixed fermentation with different microorganisms can facilitate fermentation metabolism and increase the low molecular metabolites accumulation, thereby enhancing the bioactive activity. In this study, we evaluated the immune-stimulating activities of Spirulina platensis and different extracts from fermented S. platensis (FS) by mixed probiotics in vitro, by measuring the proliferation and Th1/Th2 immunomodulatory potential on murine primary splenic lymphocytes. The results showed that mixed fermentation enhanced the immunomodulatory activity of S. platensis with higher lymphocyte proliferation compared with non-fermented S. platensis (NFS). Notably, the low molecular weight (<3kDa) peptide fraction from fermented S. platensis (L-PFS), especially at 40μg/ml, presented the strongest activity in promoting lymphocytes proliferation and modulating cytokines (IL-2 and IL-10) secretion. Meanwhile, L-PFS enhanced the relative mRNA expression of Th1 cytokine (IFN-γ) and Th2 cytokine (IL-4), along with inhibiting the relative mRNA expression of Th1 cytokines (IL-2 and TNF-α) and Th2 cytokine (IL-10) compared with Concanavalin A-treated lymphocytes. PRACTICAL APPLICATIONS: Fermentation with mixed probiotics could effectively improve the bioactive activity of S. platensis. In particular, L-PFS screened from the FS could significantly contribute to the immune-enhancing activity of lymphocytes, promote the Th1/Th2 balance, and provide insights for the investigation of FS as the potential immunomodulatory food products.

Kinetics of cellular oncogene expression in mouse lymphocytes. II. Regulation of c-fos and c-myc gene expression.

Newly isolated lymphocytes from mouse spleens express the c-fos oncogene even in the absence of mitogen with maximal mRNA levels 60 min post preparation of single cell suspension, whereas c-myc mRNA levels increase only after mitogenic stimulation with maximal mRNA levels 6 h post stimulation. The half-lives of c-fos mRNA are generally very short; they increase from 14 min (after 30 min of culture) to 70 min (after 2 h of culture). The half-lives of c-myc mRNA decrease from 50 min (at 2 and 6 h post stimulation with concanavalin A) to 12 min (at 48 h post stimulation). The c-fos gene transcription is already turned on in time-0 lymphocytes 10 min after disruption of the organ structure of the spleens and is down-regulated after 2 h and later. In nuclear run-on experiments with nonstimulated lymphocytes there is already significant transcription of the first exon of c-myc, but almost no elongation of the transcript to exon 2 and 3. In concanavalin A-treated lymphocytes elongation is stimulated about 5-fold within 6 h and returns to background levels at 48 h post stimulation. The nuclear run-on analyses of nonactivated lymphocytes showed a signal for RNA complementary to c-myc mRNA detected with a probe specific for the exon 1/intron 1 boundary of c-myc, which disappeared with increasing time of concanavalin A stimulation. This anti-sense transcription may play a role in regulating the elongation of c-myc transcripts.

Permissive effect of substratum contact on DNA synthesis in concanavalin A-treated lymphocytes.

The effects of contact with a solid surface (in the form of adhesive microcarrier beads (Cytodex)) on the induction of proliferation of human blood lymphocytes after exposure to concanavalin A (Con A) were investigated. The duration of the lag phase preceding DNA synthesis was identical in the presence and absence of beads. The kinetic course of initiation of DNA synthesis was exponential but with different rate constants both in the presence and in the absence of beads during the first 4 days of the culture period. Cytodex exerted its effect by increasing the proportion of cells initiating DNA synthesis in response to Con A. To elucidate whether lymphocytes responded to Con A exposure in a dose-dependent manner, cells were seeded at different concentrations and exposed to Con A for different times. At 36 and 48 h after start of stimulation the proportion of cells synthesizing DNA increased with increasing cell number in the cultures. In contrast, the portion of cells synthesizing DNA was markedly decreased at high cell densities 60, 72 and 96 h after start of stimulation. In the presence of microcarrier beads, however, the proportion of cells synthesizing DNA was proportional to the cell number in the cultures also after 60, 72 and 96 h.

Cellular inflammatory defenses in Legionella pneumonia

The inflammatory response in Legionella pneumonia includes important, if potentially contradictory, contributions from the alveolar macrophage and PMNL. Legionella resembles the facultative intracellular bacterial pathogens in its relationship to macrophages. The resident alveolar macrophage plays an important supportive role in the early hours after introduction of bacteria into the airspaces. A rapid recruitment of inflammatory cells—first PMNL and later mononuclear cells—occurs, although the mechanisms for recruitment of phagocytes are unknown. PMNL do not support the growth of Legionella . In fact, their appearance in the air spaces coincides with the first evidence of an effective host defense in experimental models. Monocytes and macrophages that have been activated by exposure to the supernatant of concanavalin A-treated lymphocytes can inhibit intracellular replication of the bacteria. A combination of immunologically and nonimmunologically directed host defenses may be required to control the infection definitively and eliminate Legionella from the lower respiratory tract.

Cytochrome changes in control and concanavalin A-stimulated lymphocytes

Cytochrome levels in control and concanavalin A-treated lymphocytes were quantitated using low-temperature spectroscopy (77 °K) and correlated with cell protein. Cytochrome ratios in uncultured lymphocytes of 1.00:0.28:1.86 were estimated from substrate-reduced spectra for cytochromes c, b, and aa 3, respectively. Control samples in culture showed a significant 20-h increase and 36-h decrease in cytochromes b and aa 3. These alterations are believed to be a consequence of isolation treatment and/or placement in a tissue culture environment. Concanavalin A-treated lymphocytes exhibited marked increases at 36 and 45 h in cytochrome b and dithionite-reduced cytochrome aa 3. These increases occur after the 20 h required for commitment to mitogenesis and appear to represent synchronous synthesis correlated to the G 2 phase of the cell cycle. Both control and concanavalin A-treated cells exhibited significant changes in cytochrome b 5. Mitochondrial involvement in mitogenesis is supported by evidence indicating that the mitogenic process as well as concanavalin A-induced cytochrome changes are inhibited by chloramphenicol. The changes observed in cytochrome b 5 are not significantly affected by chloramphenicol.

Concanavalin A-induced modification of the electrophoretic mobility of lymphocytes. Effect of colchicine and cytochalasin B

Concanavalin A induces redistribution, i.e. ‘capping’ and endocytosis of its receptors, on the surface of lymphocytes. This phenomenon has been shown to alter the cellular surface charge density. Colchicine, which depolymerises cytoplasmic microtubules, and cytochalasin B, which inactivates microfilaments, were used to determine the transmembrane control of the changes in the electrophoretic mobility of mouse lymphocytes. Colchicine neither inhibited nor modified the lectin-induced changes, irrespective of whether the cells were exposed to this agent before or after the interaction with concanavalin A. Pre-incubation with cytochalasin B, on the other hand, inhibited the alterations induced by concanavalin A. Cytochalasin B also reversed the altered electrophoretic mobilities of concanavalin A-treated lymphocytes. These data provide further confirmation of the relationship between lectin-induced redistribution and the electrokinetic behaviour of lymphocytes and establish that ‘capping’ but not endocytosis of the glycoprotein receptors is responsible for the electrophoretic changes.

The paradoxical effect of cycloheximide on 3H-uridine incorporation by histidine-starved concanavalin A-treated lymphocytes

Cycloheximide causes a paradoxical increase in uridine incorporation by histidine-starved lymphocytes treated with concanavalin A in a serum-free medium. The mechanism of this effect is indirect, depending on tRNA aminoacylation.

An inhibitor of tRNA aminoacylation reversibly inhibits DNA synthesis in concanavalin A-treated lymphocytes

In concanavalin A-treated lymphocytes, the synthesis of DNA can be completely inhibited by l-histidinol. an inhibitor of tRNA His aminoacylation. It is shown that this inhibition is reversible, and that. during the period of inhibition, lymphocytes progress in the G 1 phase of the cell cycle from their resting state.

864 SUPPRESSOR T CELL FUNCTION IN DIABETES MELLITUS

Autoaggression against pancreatic islet cells has been described in patients with diabetes mellitus. Based on the hypothesis that a loss of immune regulatory suppressor T cells could be important in the development of these autoaggressive reactions, we examined suppressor T cell function in 14 children with insulin-dependent diabetes mellitus. Suppressor cell activity was determined by assessing the effect of concanavalin A-treated lymphocytes on the one-way mixed leukocyte culture reaction. Suppressor cell activity was demonstrated in 15 of 15 normal controls. However, 11 of 14 patients with insulin-dependent diabetes mellitus lacked suppressor T cell function. In our sample, age, sex, duration of diabetes mellitus and control of the disease did not correlate with the presence or absence of suppressor cell activity. Our data suggest that decreased suppressor T cell function may be important in the pathogenesis of some forms of diabetes mellitus. The relationship of HLA (HLA-A,B,C,D) and suppressor T cell function in diabetes mellitus is being investigated.