Assessing resistance of sugarcane varieties to sugarcane borer Diatraea saccharalis Fab. (Lepidoptera: Crambidae).

In this study, we investigated resistance traits to the sugarcane borer Diatraea saccharalis Fab. (Lepidoptera: Crambidae) in the leaves and stalks of six sugarcane cultivars in a series of greenhouse and laboratory assays. Investigation of plant factors and infestation rates to better discriminate stalk damage by the sugarcane borer indicated that infestation of 7-month-old, single plants with 20 larvae at the third or fourth instar per plant was suitable to assess tunneling length. Three cultivars (i.e. SP803280, RB928064, and RB835486) had lower stalk damage (i.e. tunnel length) than cultivar SP891115, which exhibited relatively greater susceptibility to tunneling by the borer. The time required for the larvae to enter the sugarcane stalk was longer for cultivar SP803280, indicating resistance traits on the stalk surface, which correlated with lower stalk damage. Larvae feeding on SP813250 stalks had the lowest weight gain, indicating that this cultivar has resistance traits to larval development within its stalks. Cultivars RB867515 and SP891115 resulted in the highest mortality of early-stage larvae feeding on leaves, indicating the presence of resistance factors in their leaves. Multi-trait cluster and principal component analyses placed the cultivars into three and four clusters, respectively. The cultivars placed in different groups that exhibited resistance to leaf feeding, stalk entrance, and tunneling by the sugarcane borer could be used for crossings in sugarcane breeding programs with the goal of obtaining higher levels of resistance to D. saccharalis.

Validity of one-repetition maximum predictive equations in men with spinal cord injury.

STUDY DESIGN: Cross-sectional study. OBJECTIVES: The study aimed (a) to test the cross-validation of current one-repetition maximum (1RM) predictive equations in men with spinal cord injury (SCI); (b) to compare the current 1RM predictive equations to a newly developed equation based on the 4- to 12-repetition maximum test (4-12RM). SETTING: SARAH Rehabilitation Hospital Network, Brasilia, Brazil. METHODS: Forty-five men aged 28.0 years with SCI between C6 and L2 causing complete motor impairment were enrolled in the study. Volunteers were tested, in a random order, in 1RM test or 4-12RM with 2-3 interval days. Multiple regression analysis was used to generate an equation for predicting 1RM. RESULTS: There were no significant differences between 1RM test and the current predictive equations. ICC values were significant and were classified as excellent for all current predictive equations. The predictive equation of Lombardi presented the best Bland-Altman results (0.5 kg and 12.8 kg for mean difference and interval range around the differences, respectively). The two created equation models for 1RM demonstrated the same and a high adjusted R2 (0.971, P<0.01), but different SEE of measured 1RM (2.88 kg or 5.4% and 2.90 kg or 5.5%). CONCLUSION: All 1RM predictive equations are accurate to assess individuals with SCI at the bench press exercise. However, the predictive equation of Lombardi presented the best associated cross-validity results. A specific 1RM prediction equation was also elaborated for individuals with SCI. The created equation should be tested in order to verify whether it presents better accuracy than the current ones.

Colostrum composition of Santa Inês sheep and passive transfer of immunity to lambs.

This study aimed to analyze the chemical composition and the IgG concentration of the colostrum, transitional milk, and mature milk of Santa Inês ewes as well as the transfer of passive immunity to lambs. Thirty-two pregnant ewes and 38 lambs were used. Ewes were milked immediately after lambing and at 12, 24, 36 h and 10 d postpartum. Colostrum was provided to the lambs at 40±15 min (mean±SE) after birth and then at 30-min intervals for obtaining the intake closest to 10% of body weight, and transitional milk was provided ad libitum. Blood from the lambs was collected 36 h after birth for measuring the serum concentrations of IgG, total protein, albumin, and gamma-globulin. The production was lower in primiparous than in multiparous ewes with body condition score (BCS)<2.75, but did not differ between primiparous and multiparous with BCS≥2.75 (interaction parity and BCS). The IgG concentration and fat, protein, lactose, and defatted dry extract percentages were not affected by the BCS of the ewe at lambing or by the parity. The total solids percentage in the colostrum was higher in ewes with BCS<2.75 (interaction BCS and time). The production and the protein, total solid, and defatted dry extract percentages showed quadratic behavior, the fat percentage decreased linearly, and the lactose percentage increased linearly with time postpartum. The IgG concentration in the colostrum was not correlated with the ewe's weight or BCS at the time of lambing. Moreover, the parity, the BCS, the ewe's type of gestation, and the lamb's sex did not influence the serum concentrations of IgG, total protein, albumin, and gamma-globulin in lambs. Adequate passive immune transfer (PIT) was observed in lambs for which the IgG intake was higher than 30 g. Failure in PIT was observed in 39.5% of lambs when considering a serum IgG concentration lower than 15 mg/mL and in 21% when considering a serum total protein concentration lower than 45 mg/mL. The mean apparent efficiency of absorption was 38.10%, with values between 0.02% and 98.80%. The serum IgG concentration was correlated with the total protein concentration (according to the enzymatic colorimetric method), the gamma-globulin concentration, and the absorption efficiency. The extreme variation on apparent efficiency of absorption may have an effect on the success of PIT. Lambs should consume at least 30 g of IgG in the first 24 h of life to ensure adequate PIT.

Reproducibility and responsiveness of heart rate indexes to assess wheeling efficiency in patients with spinal cord injuries.

STUDY DESIGN: Cross-sectional study. OBJECTIVES: To measure the reproducibility and responsiveness of heart rate indexes in measuring energy expenditure during wheelchair locomotion of adults with spinal cord injury (SCI). SETTING: SARAH Rehabilitation Hospital Network-Brasilia, Brazil. METHODS: The study consecutively enrolled 35 individuals with SCI. Volunteers propelled their wheelchairs at a self-selected and comfortable velocity around a circular track. The first assessment day was a responsiveness study, in which three tests were performed, with the wheelchair weight increased randomly during the last two tests. On the second assessment day, the test was conducted without extra weight (that is, baseline conditions) for reproducibility analyses. RESULTS: All indexes demonstrated reproducibility on all statistical analyses. The Propulsion Cardiac Cost Index (PCCI) had a lower variation coefficient than the Physiological Cost Index (PCI; 8.5%, 95% confidence interval (CI) 5.8-11.2 vs 24.2%, 95% CI 16.0-32.4) and lower effect size than the Total Heart Beat Index (THBI; 0.16 vs 0.26). The PCCI also had the best responsiveness results on all statistical tests. The PCCI correlation was the largest (r=0.63, P<0.01, 95% CI 0.43-0.83, followed by PCI (r=0.53, P<0.01, 95% CI 0.34-0.72) and then the THBI (r=0.50, P<0.01, 95% CI 0.29-0.71). CONCLUSIONS: All three indexes were reproducible and responsive. However, the PCCI gave better statistical results. This index may be useful in functional diagnosis and follow-up of rehabilitation.

Validity of heart rate indexes to assess wheeling efficiency in patients with spinal cord injuries.

STUDY DESIGN: Cross-sectional study. OBJECTIVES: To validate heart rate (HR) indexes for the evaluation of energy expenditure during wheelchair propulsion in people with spinal cord injury (SCI). SETTING: SARAH Rehabilitation Hospital Network-Brasilia, Brazil. METHODS: Forty-eight men aged 29.0±7.8 years with a SCI between C6 and L3 causing complete motor impairment were enrolled in the study. The assessment consisted of 5 min of rest while seated in the wheelchair, followed by 5 min of wheelchair propulsion at a self-selected comfortable speed. The main outcomes measured were oxygen consumption, HR, physiological cost index (PCI), total heart beat index (THBI) and propulsion cardiac cost index (PCCI). RESULTS: Using oxygen uptake as gold standard, the highest correlations were found between this and PCCI (r=0.59, P<0.001, 95% confidence interval (CI) 0.36-0.75) and THBI (r=0.58, P<0.001, 95% CI 0.36-74.0), independently of the injury level. The PCI had the lowest correlation coefficient (r=0.38, P<0.01, 95% CI 0.11-0.60). Spearman correlation analysis showed that the indexes mostly associated with lesion level were PCCI (ρ=-0.531; P<0.001; 95% CI -0.708 to -0.291) and THBI (ρ=-0.524; P<0.001; 95% CI -0.704 to -0.282). CONCLUSIONS: Both THBI and PCCI seem to be valid measures for assessing energy expenditure. Both indexes showed a coherent correlation with the spinal injury level.

Determination of normative values for 20 min exercise of wheelchair propulsion by spinal cord injury patients.

STUDY DESIGN: This was a retrospective observational study. OBJECTIVE: The objective was to determine the normative values for 20 min exercise of wheelchair propulsion in spinal cord injury (SCI) subjects. SETTING: Sarah Rehabilitation Hospitals Network, Brazil. METHODS: A total of 413 medical records for SCI patients at different levels and classifications at the Sarah Rehabilitation Hospitals Network, Brazil, who performed 20 min exercise in a rehabilitation programme between the years 2004 and 2009 were consulted. Information regarding patient and performance characteristics was obtained, including distance travelled, mean velocity, rest and exercising heart rate and perceived exertion. The data were analysed by gender and by injury level group: tetraplegia (TT) or paraplegia (PP). RESULTS: The participants' ages ranged from 18 to 64 years, and the median time since injury was 1.2 years. The men and women had different performances regardless of their level of injury. The distance ranged between 495 and 2106 m for men and between 300 and 1901 m for women. The mean velocity of propulsion ranged from 25 to 105 m min(-1) for men and from 15 to 95 m min(-1) for women. CONCLUSIONS: This study provides normative data for the 20 min exercise that could be used to estimate the resistance capacity by manual wheelchair users with SCI and evaluate the effects of training and other therapeutic interventions.

Analysis of health stories in daily newspapers in the UK.

OBJECTIVES: To assess what makes a good piece of medical reporting in newspapers, to quantify what is being reported on in the major British newspapers, to identify the sources of the news threads, and to assess how these are reported. STUDY DESIGN: Development and validation of a tool to assess the quality of reporting of health-related articles, and assessment of the quality of these articles in British newspapers. METHODS: Eight national daily newspapers from the UK were reviewed for 20 days over a 2-month period. All articles reporting newly emerging research pertaining to health in humans were included and reviewed independently by two raters. A descriptive analysis was performed. Subsequently, a quality assessment tool for use by a non-expert was developed and validated to objectively assess the quality of a newspaper article on a health-related topic. RESULTS: The quality assessment tool was found to have good internal consistency and inter-rater reliability. The Daily Mail published almost twice as many articles as its nearest rival, The Daily Express, and over eight times as many articles as The Guardian. Articles in The Times were, on average, more than twice as long as those in The Sun and The Daily Telegraph. The highest quality articles were in The Times and The Independent, with the lowest quality articles in The Sun. The quality scores of anonymous articles were significantly lower than those attributed to named journalists. CONCLUSIONS: There are significant differences in the quality of reporting within and between major daily UK newspapers, with anonymous articles being the poorest quality, and widespread reliance on press releases from the major UK scientific journals.

Invasive dynamic electrical impedance myography during 100 s of moderate contraction in rats' gastrocnemius muscle.

GOAL: The present study aimed to investigate the behavior of dynamic electrical impedance myography (dEIM) signals during a 100-s period of the dynamic contraction of Wistar rats' gastrocnemius evoked by electrical stimulation and to link the variations in bioimpedance with muscular energy systems. METHODS: Muscle contraction used 30% of the maximum muscular force and persisted for 100 s, along which dynamic bioimpedance signals were acquired. Based on the bioimpedance signals, two parameters, ΔZc and ΔZpc, were calculated to allow the analysis of their changes with the energy systems that supplied adenosine triphosphate (ATP) to the muscle. ΔZc indicated the variation of impedance of a twitch cycle compared to the values observed during the rest period preceding the cycle, and ΔZpc indicated slow bioimpedance variations compared to the values obtained during the rest period. RESULTS: The results indicated that ΔZc followed the force behavior, achieving a change rate of ∼14%. This parameter was associated with instantaneous impedance changes owing to the occurrence of each twitch. CONCLUSION: Although the findings of this study were linked to energy system processes, future studies are required for improving the understanding of the underlying mechanisms involved in dEIM. SIGNIFICANCE: The results contributed to understanding the relation of energy systems that supply ATP to the muscles with dEIM variations that occurred during muscle activity.

Efficacy and safety of fluoroless ureteroscopy and retrograde intrarenal surgery for the treatment of urolithiasis: A comparative study.

INTRODUCTION: Ureteroscopy (URS) and retrograde intrarenal surgery (RIRS) are traditionally guided by fluoroscopy, but the risks of exposure to ionizing radiation may present a matter of concern for patients and urologists. The aim of this study was to evaluate the efficacy and safety of fluoroless URS and RIRS compared with conventional fluoroscopy-guided procedures for the treatment of ureteral and renal stones. MATERIAL AND METHODS: Patients treated with URS or RIRS for urolithiasis between August 2018 and December 2019 were retrospectively evaluated and grouped according to the use of fluoroscopy. Data was collected from individual patient records. The main outcomes were stone-free rate (SFR) and complications, compared between the fluoroscopy and fluoroless groups. A subgroup analysis by type of procedure (URS and RIRS) and a multivariate analysis to identify predictors of residual stones were conducted. RESULTS: A total of 231 patients met the inclusion criteria: 120 (51.9%) in the conventional fluoroscopy group and 111 (48.1%) in the fluoroless group. No significant differences were found between groups regarding SFR (82.5% vs 90.1%, p=.127) or postoperative complication rate (35.0% vs 31.5%, p=.675). In the subgroup analysis these variables did not present significant differences, regardless of the procedure considered. In the multivariate analysis the fluoroless technique was not an independent predictor of residual lithiasis (OR 0.991; 95% IC 0.407-2.411; p=.983), when adjusted for procedure type, stone size and stone number. CONCLUSION: URS and RIRS can be done without fluoroscopic guidance in selected cases, without affecting the efficacy or safety of the procedure.

Complement and antibody primary immunodeficiency in juvenile systemic lupus erythematosus patients.

OBJECTIVE: To evaluate the frequency of primary immunodeficiencies (PID) in juvenile systemic lupus erythematosus (JSLE) patients. METHODS: Some 72 JSLE patients were analyzed for levels of immunoglobulin classes and IgG subclasses and early components of the classical complement pathway. Determination of C4 gene copy number (GCN) and detection of type I C2 deficiency (D) were also performed. RESULTS: PID was identified in 16 patients (22%): C2D in three, C4D in three, C1qD in two, IgG2D (<20 mg/dl) in four, IgAD (<7 mg/dl) in three, and IgMD (<35 mg/dl) in three; one of these patients presented IgA, C2 and C4D. Two patients had low C4 GCN and two had type I C2D. Demographic data, family history of autoimmune disease and PID, JSLE clinical findings, occurrence of infections, disease activity and therapies were similar in patients with and without PID (p > 0.05). Remarkably, the median of Systemic Lupus International Collaborating Clinics/ACR-damage index (SLICC/ACR-DI) was significantly higher in JSLE patients with PID compared with patients without these abnormalities (p = 0.0033), likewise the high frequency of SLICC/ACR-DI > 1 (p = 0.023). CONCLUSIONS: A high frequency of PID was observed in JSLE patients, suggesting that these defects may contribute to lupus development. Our findings indicate that these two groups of PID should be investigated in severe pediatric lupus.

A B-cell mitogen from a pathogenic trypanosome is a eukaryotic proline racemase.

Lymphocyte polyclonal activation is a generalized mechanism of immune evasion among pathogens. In a mouse model of Trypanosoma cruzi infection (American trypanosomiasis), reduced levels of polyclonal lymphocyte responses correlate with resistance to infection and cardiopathy. We report here the characterization of a parasite protein with B-cell mitogenic properties in culture supernatants of infective forms, the cloning of the corresponding gene and the analysis of the biological properties of its product. We characterized the protein as a co-factor-independent proline racemase, and show that its expression as a cytoplasmic and/or membrane-associated protein is life-stage specific. Inhibition studies indicate that availability of the racemase active site is necessary for mitogenic activity. This is the first report to our knowledge of a eukaryotic amino acid racemase gene. Our findings have potential consequences for the development of new immune therapies and drug design against pathogens.

The Brain Metabolic Signature in Superagers Using In Vivo 1H-MRS: A Pilot Study.

BACKGROUND AND PURPOSE: Youthful memory performance in older adults may reflect an underlying resilience to the conventional pathways of aging. Subjects having this unusual characteristic have been recently termed "superagers." This study aimed to explore the significance of imaging biomarkers acquired by 1H-MRS to characterize superagers and to differentiate them from their normal-aging peers. MATERIALS AND METHODS: Fifty-five patients older than 80 years of age were screened using a detailed neuropsychological protocol, and 25 participants, comprising 12 superagers and 13 age-matched controls, were statistically analyzed. We used state-of-the-art 3T 1H-MR spectroscopy to quantify 18 neurochemicals in the posterior cingulate cortex of our subjects. All 1H-MR spectroscopy data were analyzed using LCModel. Results were further processed using 2 approaches to investigate the technique accuracy: 1) comparison of the average concentration of metabolites estimated with Cramer-Rao lower bounds <20%; and 2) calculation and comparison of the weighted means of metabolites' concentrations. RESULTS: The main finding observed was a higher total N-acetyl aspartate concentration in superagers than in age-matched controls using both approaches (P = .02 and P = .03 for the weighted means), reflecting a positive association of total N-acetyl aspartate with higher cognitive performance. CONCLUSIONS: 1H-MR spectroscopy emerges as a promising technique to unravel neurochemical mechanisms related to cognitive aging in vivo and providing a brain metabolic signature in superagers. This may contribute to monitoring future interventional therapies to avoid or postpone the pathologic processes of aging.

I-E-linked control of spontaneous rheumatoid factor production in normal mice.

The concentration of serum IgM molecules binding to IgG2a (rheumatoid factor [RF]) in solid phase assays is 10-100-fold higher in normal, unmanipulated C3H/HeJ (H-2k) than in C57BL/6 (H-2b) mice. Analysis of MHC-congenic mice with the prototype strains show that C3H SW (H-2b) are low, and B6.H-2k are high RF expressor strains, respectively. Furthermore, segregation of RF phenotypes in progenies from backcrosses to C3H/HeJ of (C3H/HeJ x C57BL/6)F1 hybrid mice shows MHC- and IgH-linked controls. RF phenotypes also segregate as if they are MHC linked in crosses between H-2-congenic strains (C3H/HeJ and C3H.SW). The study of intra-H-2 (k/b and k/s) recombinant mice suggested that RF phenotype control is linked to the I-E region. This was confirmed by the typing of C57BL/6 mice expressing a transgenic E alpha chain, and thus, I-E+, which, in contrast to nontransgenic littermates, are high expressors of RF.

Specific T helper cells that activate B cells polyclonally. In vitro enrichment and cooperative function.

C3H/HeJ T cells which specifically recognize B cell-surface antigens of the related, major histocompatibility complex-compatible C3H/Tif strain, can be substantially enriched in vitro by long-term exposure (2--6 wk) of primed lymph node cells to the relevant cellular antigens. These enriched T cells contain functional helper cells as demonstrated by their capacity to induce large numbers of Ig-secreting plaque-forming cells (PFC) in cultures of antigenic B cells. The cooperative interaction results in activation of a large fraction of all splenic B cells, with consequent exponential growth and maturation to high rate secretion of IgM, IgG1, and IgG2, but not IgG3. The IgM PFC response includes antibody specificities to a number of different antigens and can be considered, therefore, as polyclonal. The T helper cell-dependent B-cell response is insensitive to inhibition by anti-delta antibodies, and in contrast with lipopolysaccharide-induced PFC responses, is only partially sensitive to the inhibitory effects of anti-mu antibodies. Finally, B-cell activation to growth and maturation by helper T cells strictly required direct T-cell recognition of antigens on the surface of responding B cells, leading us to the conclusions that if any soluble factors are generated in the collaborative process, they are either antigen specific or incompetent to initiate B-cell growth.

Genetical control of B-cell responses. III. Requirement for functional mitogenicity of the antigen in thymus-independent specific responses.

Spleen cells from C3H/HeJ mice fail to respond with polyclonal antibody synthesis to mitogenic concentrations of lipopolysaccharide (LPS) which are optimal for activating spleen cells from a high-responder strain (B10.5M). This unresponsiveness is selective for LPS, since C3H/HeJ cells respond as normals to another B-cell mitogen, purified protein derivative of tuberculin. Spleen cells from low-responder mice also fail to mount a specific anti-NNP plaque-forming cell (PFC) response, when challenged in vitro by NNP-LPS. However, C3H/HeJ cells develop normal responses to another thymus-independent hapten conjugate, DNP-AECM-Ficoll. C3H/HeJ mice fail to mount a specific anti-LPS antibody response, when challenged in vivo with doses of soluble LPS which are fully immunogenic for the high-responder strain. However, C3H/HeJ mice develop normal direct and indirect PFC responses to LPS, when challenged with a thymus-dependent form of the immunogen. These results are interpreted as indicating as absolute requirement for functional mitogenicity of the antigen, in the induction of specific thymus-independent antibody responses.

Role of C'3 and Fc receptors in B-lymphocyte activation.

Attempts were made to identify the non-Ig lymphocyte receptor responsible for B-cell induction by antigen and polyclonal B-cell activators (PBA). As a first step, the role of C'3 and Fc receptors was analyzed. It was shown that complement could be fixed onto B cells to such an extent that the lymphocytes could not bind complement-coated red cells, but this did not result in induction of polyclonal antibody synthesis, nor did it inhibit the lymphocytes response to PBA. However, the C'3 receptros possessed a passive focussing role in the induction of polyclonal antibody responses. Thus, PBA that had fixed complement activated polyclonal responses at lower concentrations than the same substances that had not fixed complement. Most likely the dual binding of PBA molecules to B cells by the PBA and the C'3 receptors caused more PBA molecules to be bound to each cell. However, the focussing function of the C'3 receptors was several orders of magnitude smaller than that of the Ig receptors. Analogous studies were carried out with Fc receptors. Binding of different types of antigen-antibody complexes did not cause activation of polyclonal or specific antibody synthesis, nor did it significantly interfere with induction of antibody synthesis by PBA substances.

Isotype commitment in the in vivo immune responses. I. Antigen-dependent specific and polyclonal plaque-forming cell responses by B lymphocytes induced to extensive proliferation.

The random recombination and deletion hypothesis for the control of isotype commitment in antibody responses was directly tested in a serial transfer system in vivo. Normal or hyperimmune spleen cells were used in weekly serial transfers with antigen into irradiated recipients until clonal senescence was observed. Antigen-specific and -nonspecific plaque-forming cells of all isotypes were determined at each transfer time. No major changes in the isotypes of specific antibodies were observed for the whole life-span of the transferred cells (9-10 wk), and no indication was obtained for the accumulation of cells transcribing the most 3' members of the C-gene cluster with sustained proliferation. Rather, the dominant isotypes were found throughout the response to be IgG1, IgG2b, and IgG2a. The results imply isotype-specific regulatory mechanisms in the control of Ig class production. These appear to operate as well in the antigen-nonspecific component of the immune response.

Differential expression of VH gene families in peripheral B cell repertoires of newborn or adult immunoglobulin H chain congenic mice.

The pattern of VH gene family expression in the primary B cell repertoire of the mouse is strain dependent. In C57Bl/6 mice, the VH J558 family is expressed by more than 45% of the cells, while the expression of VH 7183, VH Q52, and VH 36-60 families together does not exceed 20%. In BALB/c mice, relative expression of VH J558 is lower than 35%, while the sum of the other three families reaches 25%. To assess which genetic loci control strain-specific VH gene family expression, we studied VH gene family usage in splenic B cell repertoires of different congenic strains of mice. Changes in major histocompatibility complex or immunoglobulin (Ig) K light chain genes did not modify VH gene family expression in adult mice. Differences at the IgH locus, however, modified VH gene family usage. In 1-d-old mice, the strain-specific VH gene family expression pattern is determined by the IgH haplotype. In adult mice, the VH gene family expression pattern of resting B cells is independent of the IgH locus and follows the genetic background of the congenic strain, while it is determined by the IgH haplotype among Ig-secreting spleen cells. In F1(B6 x BALB/c) mice, each of the two spleen B cell populations, sorted on the basis of mu heavy chain allotype expression, shows an independent VH gene family expression pattern, determined by the IgH locus. The implications of these results in the control of VH gene family expression, and in the selection of peripheral B cell repertoires are discussed.

Differential macrophage requirements for T helper cell and T helper cell-induced B lymphocyte proliferation.

Major histocompatibility complex-restricted helper T cell clones against "minor" antigens expressed on B cell and macrophage surfaces, when confronted with appropriate T cell-depleted spleen cells, are induced to proliferation and, in turn, activate "target-responder" B cells to polyclonal growth and maturation. Irradiation of helper cell populations, however, demonstrates that their effector functions (and B lymphocyte responses) are independent of proliferative activity. Adherent cell depletion on Sephadex G10 columns, while completely abrogating helper T cell proliferation, does not abolish helper cell-induced B cell responses, demonstrating a remarkable quantitative difference in macrophage requirements for the growth of these two cell types. Because significant B cell responses are detected upon interaction with primed helper T cells under conditions of extreme macrophage depletion, we conclude that the role of macrophages in T-B cell cooperation is limited to expansion of optimal numbers of helper T lymphocytes. It follows that activated helper cells can autonomously produce all B cell-specific growth and maturation factors mediating cooperative antibody responses. In contrast, the profound reduction of LPS-induced responses upon macrophage depletion suggests accessory cell production of such factors in thymus-independent B cell growth and/or maturation.

Mitogen-activated B-cell blasts reactive to more than one mitogen.

One of three splenic B cells of 2- to 3-mo-old C57BL/6J or C3H/Tif mice are activated either by lipopolysaccharide (LPS) or by lipoprotein (LP) to grow and to mature to IgM-secreting cells. When mitogen-activated blast cells, after a 2-d activation period, are separated from nonactivated, small cells by velocity sedimentation, and no mitogen is readded, the blasts do not continue to grow but do continue to secrete IgM for several days. When the homologous mitogen is added for restimulation, the blast cells continue for several days to divide every 18 h and to develop IgM-secreting, plaque-forming cells. Frequency analyses at limiting dilutions of reactive B-blasts show that one cell in approximately equal to 1.2--1.5 blasts continue to grow and mature in the presence of the homologous mitogen, either LPS or LP. When the B-cell blasts obtained in a first activation period with either LPS or LP are restimulated with a heterologous mitogen, LPS, LP, Nocardia mitogen or mitogens contained in fetal calf serum a high proportion of the blasts continue to grow and mature to IgM-secreting cells. Frequency analyses show for LPS- or LP-blasts, restimulated in a heterologous fashion with either LP or LPS, that one cell in 1.35--1.5 blasts continue to divide and to mature to IgM-secreting cells. C3H/HeJ-splenic B-cells, which are LPS nonresponders, can only be activated to blast cells by LP. These LP-activated blasts can be restimulated by the homologous LP and by Nocardia mitogen and mitogens of fetal calf serum, but not by LPS. The results indicate that the majority of splenic B cells of 2- to 3-mo-old C57BL/6J or C3H/Tif mice are reactive to more than one B-cell mitogen. B cells, therefore, can possess in their surface membrane multireactive mitogen-receptor complexes which regulate growth and maturation.