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Notes: Background Stings from bees and wasps can cause systemic reactions which can be fatal in some individuals. In these venom-sensitive patients, specific IgE to the venom is produced and is considered to participate in the adverse reactions. This immune response requires antigen presentation by human leucocyte antigens (HLA) class II molecules, which includes DR and DP, which are present on antigen presenting cells.Objective To test for associations between HLA class II DRB1 and DPB1 alleles and life- threatening sensitivity to both bee and wasp venoms. To establish further whether any associations are independent of the atopy phenotype.Methods A total of 33 bee- and 44 wasp-venom-sensitive patients was studied. DRB1 genotypes were determined by single stranded oligonucleotide (SSO) probing of PCR products, and DPB1 genotypes by amplified fragment length polymorphism (AFLP) analysis. Total and specific IgE were measured using the Pharmacia Immunocap, FEIA. Patients with specific IgE to the venom antigens only were termed monosensitive and those with additional specific IgE to HDM and/or GP were termed polysensitive.Results Allele frequencies were compared to an unrelated control population. The 33 bee- sensitive patients had a greater prevalence of DRB 1*07 alleles than the control subjects, 26% vs 14%, with an odds ratio (OR) of 2.1 (95%CI, 1.2–3.7, P= 0.015, corrected for multiple comparisons, pc 〉 = ns). This association was confined to the 15 monosensitive bee patients, who had a 43% DRB 1*07 allele frequency when compared with 11% in the 18 polysensitive bee patients, OR 6.1 (95%CI, 1.73–22, P= 0.004, pc= 0.05), and when compared with a control group of non-venom subjects, 43% vs 16%, OR 3.9 (95% CI, 1.72–9.0, P= 0.002, pc= 0.02). The 44 wasp-sensitive patients had an increase in the DRB1*11 allele when compared with the control subjects, 13% vs 6%, with an OR 2.2 (95%CI, 1.0–4.6, P= 0.04, pc= NS), and a decreased prevalence of DRB 1*04 alleles, 10% vs 19%, with an OR 0.33 (95%CI, 0.24–0.99, P= 0.04, pc= NS), but these were not significant when multiple comparisons were taken into account. The DPB1 alleles were not significantly different between the venom sensitive patients and the controls.Conclusion Patients monosensitive to bee venom had a significantly greater prevalence of DRB 1 *07 alleles than the non-venom, control population suggesting that IgE responses in these patients may, in part be controlled by immune response HLA class II genes. These results are also suggestive of wasp-sensitive patients having a higher prevalence of DRB1*11 and a lower prevalence of DRB 1*04 than the control population.

Notes: Responses of perennial ryegrass (Lolium perenne L.) to nitrogen (N) fertilizer application rates and timings vary widely, because water is often limiting. Yield response to N fertilizer application during autumn, late-winter and spring, and the associated efficiency of use of these inputs, was assessed under conditions of non-limiting soil moisture during two, one-year lysimeter studies in Canterbury, New Zealand. There were significant (P 〈 0·05) increases in seed and herbage yields with increasing N fertilizer application. Seed yields differed with year; greatest yields were 300 g m−2 in 1996 and 450 g m−2 in 1997. Seed head numbers (r2=0·77), seeds head−1 (r2=0·92) and herbage yield (r2=0·92) were the major determinants of seed yield in both years. Irrigation required to maintain the soil between 70% and 90% of field capacity was directly related (r2=0·94 and 0·99 in 1996 and 1997 respectively) to increases in herbage yield.Seed yield, seed quality (thousand seed weight and percentage of seed 〉 1·85 mg), efficiency of water use, efficiency of N fertilizer use and apparent N fertilizer recovery were greatest when N fertilizer was applied at a rate of 50 kg N ha−1, 50 or 100 kg N ha−1 and 150 kg N ha−1 in autumn, late-winter and spring respectively; further increases in spring N fertilizer stimulated vegetative growth, but not seed yield.As a management strategy, applying N fertilizer to match the N requirements of the crop during the reproductive stage of growth will result in high yields of high quality seed while minimizing environmental impact.