Human recombinant IL-3 is a growth factor for normal B cells

IL-3 is a well known hemopoietic cell growth and differentiation factor. However, its functional role in normal B cell differentiation has not been established. We have investigated the effect of IL-3 on the growth and differentiation of human B cells. IL-3 enhanced the proliferation of Staphylococcus aureus Cowan 1 strain-stimulated B cells. The optimal time of IL-3 to stimulate B cell growth was on day 2 to day 3, suggesting that IL-3 was a B cell growth factor acting in the late stage. IL-3 synergized with IL-2 to enhance B cell proliferation and differentiation. Pretreatment of B cells with IL-3 for more than 3 days increased the expression of IL-2R on B cells. However, pretreatment of B cells with IL-2 did not alter the subsequent response to IL-3, suggesting that the synergy between IL-2 and IL-3 may be attributed to the up-regulation of IL-2 response by IL-3. In addition, pretreatment of B cells with IL-4 decreased subsequent response of B cells to IL-3 as well as IL-2, suggesting that IL-3- and IL-2-responding cells passed a similar way during the early stage of B cell activation. It appears that IL-3 and IL-6 mediate normal B cell differentiation via separate mechanisms. IL-3-induced B cell differentiation was mainly mediated by increasing cell growth, whereas IL-6 induced B cell differentiation without affecting proliferation.

Human recombinant IL-3 is a growth factor for normal B cells

IL-3 is a well known hemopoietic cell growth and differentiation factor. However, its functional role in normal B cell differentiation has not been established. We have investigated the effect of IL-3 on the growth and differentiation of human B cells. IL-3 enhanced the proliferation of Staphylococcus aureus Cowan 1 strain-stimulated B cells. The optimal time of IL-3 to stimulate B cell growth was on day 2 to day 3, suggesting that IL-3 was a B cell growth factor acting in the late stage. IL-3 synergized with IL-2 to enhance B cell proliferation and differentiation. Pretreatment of B cells with IL-3 for more than 3 days increased the expression of IL-2R on B cells. However, pretreatment of B cells with IL-2 did not alter the subsequent response to IL-3, suggesting that the synergy between IL-2 and IL-3 may be attributed to the up-regulation of IL-2 response by IL-3. In addition, pretreatment of B cells with IL-4 decreased subsequent response of B cells to IL-3 as well as IL-2, suggesting that IL-3- and IL-2-responding cells passed a similar way during the early stage of B cell activation. It appears that IL-3 and IL-6 mediate normal B cell differentiation via separate mechanisms. IL-3-induced B cell differentiation was mainly mediated by increasing cell growth, whereas IL-6 induced B cell differentiation without affecting proliferation.

[Preparation of compound membrane of traditional Chinese medicine for mouth ulcer]

The compound membrane of traditional Chinese medicine for mouth ulcer, which is made of drug-containing membrane and covering membrane, is a new type of preparation of traditional Chinese medicine. The comparison of different prescriptions and membrane materials in the preparation, adhesion and drug release of the membrane has shown that that PVA17-88-CMCNa (1:1) and PVA17-88 act best as the base of drug-containing membrane and covering membrane material respectively.

[An epidemiologic survey on a type E hepatitis (HE) outbreak]

This article deals with a HE outbreak, which occurred in Sulagong Village, Pan-jin Township, Yining County, Xinjiang. There was a total of 214 patients involved in the village, with an attack rate of 6.15 percent. Among the patients young people formed the majority. The attack rate between 20 to 24 years of age reached 17.9 percent. Attack rate of pregnant women between 18 to 35 years of age was significantly higher than that of the non-pregnant ones. The condition in pregnant patients was rather severe. Their case fatality rate was 5.88 percent and abortion rate was 17.64 percent. By epidemiological investigation, it was shown that the chief contributing cause of the HE outbreak was probably contaminated drinking water, and direct or indirect contact with the patients in the infectious stage was also a risk factor.

IL-4 blocks the up-regulation of IL-2 receptors induced by IL-2 in normal human B cells

A negative influence of IL-4 on the IL-2-induced B cell proliferation and differentiation has recently been reported. In this study, we have further investigated a role of IL-4 on human tonsillar B cell proliferation and IL-2R expression. IL-4 enhanced Staphylococcus aureus Cowan 1 strain (SAC)-induced B cell proliferation, reaching the peak on day 3. However, from day 4, IL-4 inhibited IL-2-induced proliferation. In the cross-linking study, IL-4 enhanced the density of 125I-IL-2-binding protein at low affinity binding condition (2 nM of 125I-IL-2) in SAC-activated B cells. However, IL-4 blocked the enhancement in the density of 125I-IL-2-binding proteins induced by IL-2, from day 3, in both high (50 pM of 125I-IL-2) and low affinity binding conditions, suggesting that IL-4 is able to block IL-2-induced IL-2R up-regulation. This was confirmed by a binding study: B cells that cultured for 3 days with SAC plus IL-2 expressed an average of 180 +/- 20 high affinity receptors/cell with a Kd of 12 pM and 5800 +/- 500 low affinity receptors/cell with a Kd of 980 pM. By coculturing with IL-4, high affinity receptors were almost undetectable and the expression of low affinity receptors was reduced by more than 80%. IL-4-mediated inhibition of IL-2-induced IL-2R expression does not seem to be due to the direct interaction between IL-4 and cell surface receptors, inasmuch as preincubation of cells with IL-4 for 60 min at 37 degrees C did not alter the binding of 125I-IL-2 to cells previously cultured for 3 days with SAC plus IL-2. These data suggest that IL-4 has a capacity to block the up-regulation of the high as well as low affinity IL-2R-induced by IL-2 in normal human B cells, and could provide a possible explanation for the decreased responsiveness of B cells to IL-2 in the presence of IL-4.

IL-4 blocks the up-regulation of IL-2 receptors induced by IL-2 in normal human B cells

A negative influence of IL-4 on the IL-2-induced B cell proliferation and differentiation has recently been reported. In this study, we have further investigated a role of IL-4 on human tonsillar B cell proliferation and IL-2R expression. IL-4 enhanced Staphylococcus aureus Cowan 1 strain (SAC)-induced B cell proliferation, reaching the peak on day 3. However, from day 4, IL-4 inhibited IL-2-induced proliferation. In the cross-linking study, IL-4 enhanced the density of 125I-IL-2-binding protein at low affinity binding condition (2 nM of 125I-IL-2) in SAC-activated B cells. However, IL-4 blocked the enhancement in the density of 125I-IL-2-binding proteins induced by IL-2, from day 3, in both high (50 pM of 125I-IL-2) and low affinity binding conditions, suggesting that IL-4 is able to block IL-2-induced IL-2R up-regulation. This was confirmed by a binding study: B cells that cultured for 3 days with SAC plus IL-2 expressed an average of 180 +/- 20 high affinity receptors/cell with a Kd of 12 pM and 5800 +/- 500 low affinity receptors/cell with a Kd of 980 pM. By coculturing with IL-4, high affinity receptors were almost undetectable and the expression of low affinity receptors was reduced by more than 80%. IL-4-mediated inhibition of IL-2-induced IL-2R expression does not seem to be due to the direct interaction between IL-4 and cell surface receptors, inasmuch as preincubation of cells with IL-4 for 60 min at 37 degrees C did not alter the binding of 125I-IL-2 to cells previously cultured for 3 days with SAC plus IL-2. These data suggest that IL-4 has a capacity to block the up-regulation of the high as well as low affinity IL-2R-induced by IL-2 in normal human B cells, and could provide a possible explanation for the decreased responsiveness of B cells to IL-2 in the presence of IL-4.

Recombinant interleukin (IL) 2-induced human B cell differentiation is mediated by autocrine IL6

The molecular mechanism of the interleukin (IL) 2-induced differentiation of human B cells has been investigated. The experimental results show that Staphylococcus aureus Cowan strain I (SAC) activation alone induces IL6 secretion from B cells. When B cells were activated by SAC, there was an increased transcription of the IL6 mRNA. It reached the peak level by 6 h and rapidly decreased to an undetectable level within 24 h. The IL6 concentration in the culture supernatants reached the peak at 24-48 h and decreased slightly in the following culture periods. Since IL 2 alone could induce IgG secretion, whether exogenous IL6 was added or not, and IL2 did not increase autocrine IL6 synthesis, it appears that IL2 induces the IL6 responsiveness of SAC-activated B cells to differentiate in the later stage of the culture. The addition of polyclonal anti-IL6 antibody inhibited IgG secretion. The antibody still efficiently blocked IgG secretion up to day 5, indicating an important role of autocrine IL6 in the IL2-driven B cell differentiation. However, the saturation dose of anti-IL6 antibody inhibited 50%-70% of IgG secretion, suggesting that IL2-induced B cell differentiation appears to be mediated by other factors besides IL6.

Functional roles of gamma interferon in proliferation and differentiation of human B cell subpopulations

We have studied the function of interferon-gamma (IFN-gamma) on human B cell proliferation and differentiation. When B cell subpopulations were separated by Percoll gradient centrifugation and stimulated by Staphylococcus aureus Cowan I (SAC), these subpopulations responded differently to lymphokines. Small B cells (60/80% Percell) were stimulated to proliferate by IFN-gamma alone. Large B cells (50/60% Percoll) did not respond to IFN-gamma but proliferated in response to B cell growth factor (BCGF) free of interleukin-2 (IL-2) and IFN-gamma. Although IFN-gamma alone could not induce the differentiation of SAC-activated B cells and did not support the growth of large B cells, it enhanced the proliferation and differentiation of both subpopulations in the presence of BCGF and IL-2. Also, IFN-gamma induced the expression of IL-2 receptor on B cells. Pretreatment of B cells with IFN-gamma for 48 h had a minor effect on the proliferation but significantly enhanced the differentiation in the presence of BCGF and IL-2; therefore, IFN-gamma may act as a differentiation factor. However, in a late stage of culture, IFN-gamma inhibited B cell differentiation. Our experimental data suggest that IFN-gamma is a growth factor for distinct subpopulation of SAC-activated human B cells and enhances the proliferation and differentiation and the expression of IL-2 receptor on B cells.

Distinct culture requirements for activation and proliferation of human peripheral blood B lymphocytes by Staphylococcus aureus Cowan strain and growth factors

The concentration of fetal calf serum (FCS) and the culture period were the crucial culture conditions in measuring B cell growth factor (BCGF) and IL-2 activity in vitro. Higher concentrations of FCS (10-15%) significantly inhibited BCGF activity; whereas, lower concentrations of FCS (less than 2.5%) were not sufficient for the response to IL-2. Kinetic experiments showed that the culture period for BCGF should be shorter than that for IL-2, while BCGF in combination with IL-2 induced a synergistic proliferation of B cells in a longer culture period. Adding BCGF after 48 h of SAC stimulation reduced the reaction. Hence, the conventional method using preactivated B cells does not measure BCGF but mostly IL-2. Furthermore, minute amounts of BCGF activity can be more sensitively determined by co-culturing with fixed amounts of IL-2.