First Report of Pilidium concavum Causing Tan-Brown Rot on Strawberry Fruit in Belgium.

In April 2010, pink-orange spore masses that later turned brown were observed on 7 to 50% of the transplant lots during a routine screening of Belgian strawberry (Fragaria × ananassa, cv. Elsanta) for the latent presence of Colletotrichum acutatum using the petiole freeze method (4). These spore masses contained hyaline, canoe-shaped to allantoid conidia (mean size 7.5 × 1.8 µm), which is not consistent with C. acutatum spore morphology. Subsequently, a spore mass was transferred onto potato dextrose agar (PDA) and a gray-to-brown colony with whitish, aerial mycelium was produced, which is also not consistent with C. acutatum isolates. To identify the fungus, the ITS1-5.8S-ITS2 rDNA region was amplified by PCR and sequenced. The 485-bp region was 100% identical to that of Pilidium concavum specimen voucher BPI 1107275 (GenBank Accession No. AY487094). P. concavum (Desm.) Höhn. (synanamorph Hainesia lythri; teleomorph Discohainesia oenotherae) is a pathogen of strawberry causing tan-brown rot of fruit and is a common secondary invader of roots and dead strawberry plant parts (3). A recent strain of P. concavum from strawberry, isolate UPL 50, obtained from Brazil (L. Zambolim, Univ. Fed. de Viçosa, personal communication) showed similar colony, microscopic (mean spore size of 6.8 × 1.8 µm), and molecular (ITS sequence 98% identical to that of P. concavum specimen voucher BPI 1107275) features as the Belgian isolate. Pathogenicity tests were conducted on mature strawberry fruits by submerging 15 fruits per isolate for 3 min in a conidial suspension (2 × 106 conidia ml-1 of water) obtained from a 2-week-old colony on PDA. Controls were submerged in sterile distilled water. The inoculated fruits were incubated in a moist chamber at 25°C. Sunken, yellowish brown lesions with pink and later orange-brown spore masses were observed starting 3 days after inoculation on 88 and 94% of the fruit for the Brazilian and Belgian isolate, respectively. The control fruits remained healthy. The fungal isolates were reisolated from symptomatic fruits and their identity was confirmed based on morphological features. During a strawberry field survey in July 2010 in Sint-Truiden (Belgium), lesions typical of those described above were observed on eight strawberry fruits (cv. Elsanta). The fungus was isolated from the symptomatic tissue of two fruits and characterized as described above. Since P. concavum was latently present on strawberry transplants and caused disease on the fruits in the field, we conclude that P. concavum is a potential threat for Belgian strawberry production. Moreover, no strawberry cultivars with resistance to the pathogen have been reported. The disease has previously been reported on strawberry in South America and Poland (1,2), but to our knowledge, this is the first report of P. concavum on strawberry in Belgium. Although the spore and colony morphology of P. concavum is different from C. acutatum, the spore masses of P. concavum can easily be confused with the spore masses of C. acutatum when using the freeze method. This suggests the need for microscopic analysis of these spore masses during routine analyses. References: (1) L. Cedeno et al. Interciencia 26:113, 2001. (2) U. P. Lopes et al. New Dis. Rep. 21:7, 2010. (3) J. L. Maas. Compendium of Strawberry Diseases. The American Phytopathological Society St. Paul, MN, 1998. (4) J. C. Mertely and D. E. Legard. Plant Dis. 88:407, 2004.

Evaluation of Six Models to Estimate Ascospore Maturation in Venturia pyrina.

Estimates of ascospore maturity generated by models developed for Venturia pyrina in Victoria, Australia (NV and SV), Oregon, United States (OR), and Italy (IT) or for V. inaequalis in New Hampshire, United States (NH-1) or modified in Norway (NH-2) were compared with observed field ascospore release of V. pyrina from 21 site-year combinations. The models were also compared with ascospore release data from laboratory assays. In the laboratory assays, the forecasts of the NH-1 and NH-2 models provided the best fit to observed spore release. Under field conditions, the lag phases and slope coefficients of all models differed from those of observed release of ascospores. Identifying the precise time of bud break of pear to initiate degree-day accumulation was problematic at both Australian sites. This resulted in a higher deviance between bud break and first released ascospore compared with the sites in Norway and Belgium. Linear regressions of observed release against forecasted maturity generated similarly high concordance correlation coefficients. However, where differences were noted, they most often favored models that included adjustment for dry periods. The NH-2, IT, and NV models using pooled data also provided the most accurate estimates of 95% ascospore depletion, a key event in many disease management programs.

Experimental autoimmune thyroiditis. In vitro cytotoxic effects of T lymphocytes on thyroid monolayers.

Effector mechanisms in experimental autoimmune thyroiditis (EAT) were studied in vitro by establishing a cytotoxicity system with thyroid target cells. Lymph node cells (LNC) from popliteal and inguinal lymph nodes were obtained from CBA/J mice (8-10 wk old) 12-18 d after immunization with 120 micrograms mouse thyroglobulin (MTg) in complete Freund's adjuvant (0.2 ml to both hind footpads and thighs) and were cultured with MTg (10-50 micrograms/ml). On day 5 of culture, viable LNC were added to labeled thyroid monolayers and their cytoxicity was assayed after 16 h. Functional thyroid target cells, as reflected by MTg production for up to 9 d, were prepared by adding 1 mM dibutyryl adenosine 3',5'-cyclic monophosphate and 60 microU thyroid-stimulating hormone/ml to the culture medium. On days 5-7, confluent monolayers were labeled with 111In and used as targets. Specific 111In-release ranged from 56 to 85%. The cytotoxic response is MTg specific and H-2 restricted. Pretreatment of thyroid target cells with rabbit antiserum to MTg completely inhibited cytotoxicity. Pretreatment with mouse antiserum to either Kk or Dk products resulted in approximately 50% inhibition, whereas the combined use of both antisera led to total inhibition. No cytotoxicity was observed when control BALB/c thyroid cultures were the target cells. The kinetics of the expansion of Thy-1+ cytotoxic cells by in vitro exposure to MTg were then studied. The cytotoxic response required 5 d to develop and was abolished by treating LNC on day 4 with monoclonal antibody to Lyt-1.1, but not to Lyt-2.1, plus complement. In contrast, by day 5, cytotoxicity was abrogated by similar treatment with antiserum to Lyt-2.1, but not to Lyt-1.1. We conclude that cytotoxic cells derived from MTg-immunized mice are Lyt-2-bearing cells but require the presence of Lyt-1-bearing cells for their generation and/or differentiation.

Epidemiological research of twig scab on pear as basis for a rational and ecological disease management.

Scab is one of the key parasites in fruit growth. In favourable weather conditions for the pathogen, a complete harvest can be destroyed if no control measurements are undertaken. The scab fungi on pear and apple are two distinct species. They have, however, a similar biological cycle. Despite the similarities, there are also clear differences and these differences are significant for the control of the pathogen. Pear scab does not only infect fruit and leaves as apple scab does, but also infects twigs. Especially in organic fruit growing, twig scab is a big problem. Once twig scab occurs, it seems to be impossible to get rid of scab in these orchards. The only possibility for the fruit grower in this case is a strict spraying schedule to ensure no further spread of the infection. The main goal of the project is a thorough study of the pear scab fungi (biology, sensitivity of different plant parts and cultivars, dispersal of the fungi and infection conditions, the pathogenicity and characterization of different biotypes) to unravel the life of the fungi and to develop a better control strategy. A better control strategy means a reduced fungicide use and a reduction of fungicide residue on the fruits at harvest, without a reduction of the quality of the fruits and cost effectiveness for the fruit grower. Special attention in the project goes to the role and the control of twig scab. The first results of this project will be shown.

Screening preharvest/postharvest strategies to prevent fruit rot decay.

In fruit growing preharvest sprayings in the orchard are mainly applied to protect fruit from decaying. Next to multisite fungicides (captan, thiram, tolylfluanid) the most commonly used products recognized for the Belgium market are Bellis (pyraclostrobin & boscalid) and the combination of Topsin M (thiophanate-methyl) and Frugico (diethofencarb). In general the spraying schedule varies depending on weather conditions (infection risk), preharvest interval of available fungicides, fruitgrower and cultivar of pome fruit (apple/pear). Facing the climatological conditions before picking the residue loading on the fruit surface can differ enormously. Also wet (pre)grading is considered to decrease the product residue resulting to fruits which are less protected before entering the cold storage room. In this context a partially replacement of the preharvest treatments by one postharvest application could offer a reliable alternative to the PPP reduction program (Plant Protection Products) in the orchard. A standardized application method by dipping or drenching will cover the fruits homogenically resulting in a rationalized fungicide use compared to the preharvest sprayings in the orchard. For the Belgium market Philabuster (imazalil & pyrimethanil) is registered for postharvest treatments since for this product a proper solution for the waste water of postharvest uses was developed to protect surface waters (Funds technology). Philabuster provides an advanced mould control towards fruit rot pathogens Gloeosporium spp., Botrytis cinerea and Penicillium spp. In this context several trials were set up to evaluate the biological efficacy of Philabuster alone or in combination with preharvest sprayings in the orchard. In concrete different preharvest spraying schedules were applied in the last six weeks before harvest on apple and pear facing parameters as rational fungicide use, antifungal effectiveness and cost price. The purpose was to select the optimal combination in use of preharvest fungicides with Philabuster as postharvest treatment, which offer full protection towards all key pathogens in apple and pear.

Evaluation of the users value of salts against apple scab and powdery mildew for the integrated fruit production.

As new fungicides are mainly unisite action fungicides, the problem of fungicide resistance development is becoming more important every year. Combining chemical fungicides, which is the best anti-resistance strategy, is not always possible or recommended in the case when the number of available chemical fungicides are limited or a reduction in fungicide use is asked for. Therefore the use of salts as an anti-resistance strategy was looked upon. The salts evaluated were K(HCO3), KH2PO3, KHPO4 and K2SiO3. When using these salts as an anti-resistance strategy the efficacy obtained when spraying the compounds alone was often to low to be used in rotation with chemical fungicides. Only with K(HCO3)2 a good efficacy can be observed in some years. The variation in efficacy with K(HCO3)2 observed is higher for powdery mildew. Chitosan was also included in the trials against powdery mildew, however chitosan had no effect on the infestation.

Towards high-resolution laser ionization spectroscopy of the heaviest elements in supersonic gas jet expansion.

Resonant laser ionization and spectroscopy are widely used techniques at radioactive ion beam facilities to produce pure beams of exotic nuclei and measure the shape, size, spin and electromagnetic multipole moments of these nuclei. However, in such measurements it is difficult to combine a high efficiency with a high spectral resolution. Here we demonstrate the on-line application of atomic laser ionization spectroscopy in a supersonic gas jet, a technique suited for high-precision studies of the ground- and isomeric-state properties of nuclei located at the extremes of stability. The technique is characterized in a measurement on actinium isotopes around the N=126 neutron shell closure. A significant improvement in the spectral resolution by more than one order of magnitude is achieved in these experiments without loss in efficiency.

Effect of a mouse mammary tumor virus-derived protein vaccine on primary tumor development in mice.

The vaccines used in this study were derived from purified murine mammary tumor virus (MuMTV) preparations. Approximately 60% of the protein fractions consisted of the major viral membrane glycoprotein gp52. Inoculation sc of 10 microgram MuMTV-S-derived vaccine significantly delayed the appearance of primary mammary tumors in GR and BALB/cfC3H mice (strains with high incidences of mammary cancer); in BALB/c and C3Hf mice, which have a moderate tumor incidence at an advanced age, this treatment resulted in a slight and substantial acceleration, respectively, of primary tumor development. The induced cellular immune reactivity for vaccination, as measured with the in vivo Winn test and the in vitro leukocyte adherence inhibition assay, was strongest in the GR strain as compared to the BALB/c strain. The titer of antibodies to tumor cells, as estimated by membrane immunofluorescence, was also higher in the GR strain. In BALB/cfC3H mice, the influence of different vaccination schemes with an MuMTV-O-derived protein vaccine on primary tumor development was studied. Before sc injection, the vaccine was precipitated on alum. A dose of 10 microgram vaccine resulted in a 61% decrease in tumor incidence. Two or five additional booster injections with 1 microgram protein vaccine had no beneficial effect, although the amount of antibody measured was increased after boosting.

Alternatives to copper in Scab control affect mineral composition in leaves and fruits of apple varieties with reduced Scab susceptibility or Scab resistance.

Scab (Venturia inaequalis) is the principal disease endangering both integrated and organic apple production. Scab pressure tends to build up over the years and organic farmers rely mainly on copper and sulphur treatments for control. The use of Cu in crop protection received scrutiny in recent years as this metal tends to accumulate in soil and substrates. A number of alternative organic control substances have been proposed, with variable success in scab control. We investigated the effect of these alternative organic scab control measures on several apple varieties with low scab susceptibility. The choice of scab treatments had important effects on the mineral composition of leaves and fruits. As these values affect current and future yield in perennial crops, as well as storage quality, the use of certain scab control agents requires corrective application of nutrients during and in-between growth seasons.

Brown spot control on pear: infection models versus the inoculum pressure in Belgium.

Stemphylium conidia and Pleospora ascospores were monitored in pear orchards in the region of Haspengouw in Belgium during the infectious periods of brown spot disease (end May - end August) in the years 2002, 2004 and 2005. The seasonal and daily dynamics of the captured fungal spores are discussed and a correlation analysis was performed to determine possible correlation with weather parameters. Furthermore the fungicide cover obtained by spraying upon climatological infection risk is compared with the inoculum pressure in the orchards. Pleospora ascospores were found until the end of May and discharge took place during rain events at the same time-points when Venturia inaequalis ascospores were detected. Although the fungi ejected during the same time period, the relative importance of the different spore peaks differed. The first conidia were detected at the end of May. After that date conidia were found almost every day. Seasonal dynamics of the conidia clearly differed between the years and also the number of spores retrieved differed. No spores were found below 7.5 degrees C and only at a temperature above 12.5 degrees C an increase in conidia was observed. When looking at the daily dynamics, a significant negative correlation was found between the aerial spore concentration and relative humidity and leaf wetness, and a significant positive correlation with wind, temperature and water vapor pressure deficit. When spraying upon a BSP-cast CR threshold value of 0.4, all days with spore discharges above 3 conidia/m3/day were covered in 2002 and 2004. In 2005, a year with very low infection risk and infestation, two periods with high spore discharge were not covered. The observations made show that incorporation of the inoculum pressure into the infection models will probably not lead to a big improvement of the infection models.

Folding of terminal histone-H1 peptides in the presence of the oligonucleotide 5'-(AT)6-3'.

Peptides H1(1-16) H1(204-218) of human histone H1, comprising the terminal parts of the N- and C-domain, and H1(120-210), comprising the entire C-domain of calf thymus H1, were studied using CD spectroscopy in the presence of trifluoroethanol (TFE) and the oligonucleotide 5'-(AT)6-3'. TFE induces a strong negative ellipticity at 220 nm, showing that the H1 fragments are capable of helical folding. The CD spectrum of free (AT)6 shows strong negative and positive absorptions in the 200-300 nm region resembling the psi-spectrum of DNA. Free (AT)6 showed no helix-coil transition and remained single stranded at room temperature. Combinations of the H1 peptides with increasing concentrations of (AT)6 in low-ionic-strength phosphate buffer developed a strong negative ellipticity at 235 nm. This ellipticity increased with rising (AT)6 concentration and diminished when the (AT)6 concentration exceeded the 1:1 molar ratio in H1(1-16) and H1(204-218) and the 2:1 molar ratio in H1(120-210). The 235 nm ellipticity is attributed to a complex of the H1 peptide with (AT)6 in which the protein is helical. Interaction between histone peptide and (AT)6 is also indicated by UV-absorption spectra which show that the 260 nm absorption is decreased and the 280 nm absorption is increased as compared to free (AT)6. The free peptides show no absorption in this window. The altered 260 and 280 nm absorption suggests that the single-stranded (AT)6 assumes a left-handed pitch and this is confirmed by the displacement of the 270 nm positive ellipticity of free (AT)6 towards 260 nm. Implications of a left-handed linker DNA for chromatin function are discussed.

A new post-harvest fungicide to control fruit rot on apple and pear.

PHILABUSTER is a new post-harvest fungicide developed by Janssen Pharmaceutica N.V.. It provides an advanced mould control by post-harvest treatments of citrus and pome fruit. The product is formulated as a stable suspension concentrate intended for dilution in water before use. PHILABUSTER 400 SC contains 200 g/L imazalil and 200 g/L pyrimethanil. Both active ingredients have a different single site mode of action. Imazalil inhibits ergosterol biosynthesis (DMI), whereas pyrimethanil interferes with fungal enzyme secretion and methionine biosynthesis. Due to the combination of these low risk fungicides a good anti-resistance management can be obtained. In case of existing reduced sensitivity of a population to DMI or MBC fungicides, no cross-resistance with pyrimethanil was observed. PHILABUSTER showed good activity by post-harvest treatment against key pathogens on apple and pear Penicillium expansum (blue mold), Botrytis cinerea (gray mold) and Gloeosporium spp. (lenticel rot) in small and large scale experiments with artificial or natural infections. By dip treatment of large volumes of fruit (up to 50 tons) the depletion of both active ingredients in the treatment water was low, both when plastic or wooden bins were used. Lower dose rates resulted in an inferior and inconsistent residue level of both active ingredients on fruit. Possible advantages of post-harvest treatments versus field treatments for the control of storage diseases are discussed.

Botrytis infection warnings in strawberry: reduced enhanced chemical control.

The fungal pathogen Botrytis cinerea is the causal agent of grey mould, the most important fungal fruit rot disease in strawberry in Europe. Currently disease control for grey mould is based on preventive spraying every five to seven days during flowering and harvest. Replacing preventive spraying with applications based on infection warnings can optimize performance and reduce the amount of sprays needed. Success of this approach will depend on the accuracy of the model used to predict disease outbreak. For this reason three infection models (BOTEM, BoWaS, DSS-Italy) were evaluated during the growth seasons of 2003 and 2004. The experiments included June bearing, retarded June bearing and ever bearing strawberries. In all experiments the use of infection models leaded to a reduced number of fungicide applications. However the efficacy of the different models towards the control of B. cinerea also decreased compared to the efficacy obtained with a standard 7 day schedule. Best results were obtained with BOTEM, developed by HRI (Horticultural Research International, East-Malling, UK): 17-60% reduction in fungicide use and an efficacy between 66-93 depending on the growth season, culture practice and the fungicides used. Compared with routine preventive spraying, the Botrytis fruit rot percentage is slightly higher. A higher efficacy with Botrytis infection warnings can only be obtained if infection warnings change from curative to preventive. A retroactive evaluation of a preventive warning system was included. Making use of the 48h weather forecasts supplied by the Royal Meteorological Institute of Belgium (KMI) based on ALADIN for the region of Haspengouw, it was possible to replace 30 up to 100% of the curative application by preventive spraying depending on the experiment and the threshold set for the preventive model.

Determination of co-expression of activation antigens on proliferating CD4+, CD4+ CD8+ and CD8+ lymphocyte subsets by dual parameter flow cytometry.

The incidence of activation markers on proliferating CD4+, CD4+ CD8+ and CD8+ lymphocyte subsets was determined in a single laser Epics-C fluorescence-activated cell sorter system, using a series of double staining combinations. Experiments were performed after 3 days of culture with PHA on cell fractions enriched for CD4+ or CD8+ lymphocytes before initiation of culture. The percentage of CD4+, CD4+ CD8+ and CD8+ lymphocytes in the total population was determined using double staining with Leu3 PE for the detection of CD4+ cells, and Leu2 FITC for the detection of CD8+ cells. Next, double stainings with Leu3 and Leu2 antibodies conjugated with PE and antibodies directed against activation markers (M) IL-2 receptor, transferrin receptor, HLA-DR antigen and CALLA conjugated with FITC were performed, using the following combinations: Leu3 and Leu2/M, Leu3/M and Leu2/M. The expression of activation markers on CD4+ CD8+ lymphocytes was calculated from the results. Our findings indicate that CALLA is expressed on most CD4+ and all CD4+ CD8+ cells, and on a small percentage of CD8+ lymphocytes; the IL-2 receptor was expressed on most CD4+ cells, on approximately three-quarters of CD4+ CD8+ cells and half the CD8+ cells; HLA-DR was expressed on a small percentage of CD4+ cells, all CD4+ CD8+ cells and half of CD8+ cells. The transferrin receptor was almost exclusively expressed on CD4+ CD8+ cells. The standard deviation of the calculated values did not exceed 13% and this analysis can generally be applied to determine the co-expression of a third marker in a mixture of single and double stained cells using conventional methods.

A unique African HLA haplotype may identify a population at increased risk for kidney graft rejection.

We determined HLA-A, -B, and -DR allele frequencies in kidney transplant recipients in relation to graft survival. Most recipients and donors were from African descent. The frequency of HLA-A30 was somewhat increased in recipients who rejected the graft. The frequency of HLA-B42 was significantly (P=0.002) increased in recipients who rejected the graft. Similar results were found for the HLA-DR3 allele; however, this effect was diminished when B42-, DR3+ individuals were analyzed. We further investigated the effect on transplant outcome of a unique African haplotype A30, B42, DR3, and of segments thereof, which have a high frequency in the local population. Log-rank analysis revealed that the negative effect on transplant outcome was least in A30-, B42+ recipients (P=0.417) and most pronounced in A30+, B42+ patients (P=0.006). We postulate that the negative effect on transplant outcome may reside in the A30, B42 segment of chromosome 6 and may be caused by a stronger than average immunoregulatory gene.

Analysis of absolute T helper cell number and cellular immune defects in HIV antibody positive and negative homosexual men.

To investigate if serial measurement of T helper (CD4) lymphocyte number in peripheral blood is of prognostic value, we determined lymphocyte function in asymptomatic and symptomatic HIV antibody positive and negative homosexual males and related the results to absolute number of CD4 lymphocytes in peripheral blood. Lymphocyte function was determined by measuring streptolysin O (SLO)-induced proliferative responses of peripheral blood lymphocytes (PBL) and of PBL depleted of CD8 lymphocytes. Phytohemagglutinin (PHA) induced interleukin-2 (IL-2) production was also measured. In all functional tests values were significantly lower in HIV antibody-positive subjects than in HIV antibody-negative subjects. Results lower than the 95% confidence limit in HIV antibody-negative individuals were therefore defined as "decreased." Decreased functional responses were most frequent (83-100%) in individuals with a number of CD4 lymphocytes of less than 400/microliters, and were least frequent (3-21%) in subjects with a CD4 lymphocyte count of greater than 600/microliters. Frequency of decreased functional responses was intermediate in the population with 600-400/microliters CD4 lymphocytes. The magnitude of functional responses differed significantly between groups with less than 400, 400-600, and greater than 600 CD4 lymphocytes per microliter, indicating that T helper cell number decreases with loss of immune function.

Epitope recognition in histone H1 by SLE autoantibodies in the presence of a DNA-ligand.

To investigate the specificity of anti H1 antibodies peptides from the N- and C-domain of H1 and the synthetic oligonucleotide (AT)6 were complexed. Circular dichroism (CD) spectroscopy indicated that the free peptides H1(1-16), H1(204-218) and C(121-210) in low salt buffer assume a random structure but become helical when bound to the oligonucleotide. The structured and unstructured H1 fragments were then analyzed by enzyme linked immunosorbent assay (ELISA) with anti-H1 antibodies in sera from patients with systemic lupus erythematosis (SLE) and with the monoclonal anti-H1 antibody MRA-12 derived from MLR lpr/lpr autoimmune mice. Binding of these antibodies to H1(204-218) and C was inhibited to a level of 50% when these H1 peptides were complexed with (AT)6. When the same antibody was tested with H1 fragment GC(34-210), attachment to oligonucleotide (AT)6 did not influence antibody binding. Competition studies with liquid phase GC and C antigen against solid phase GC and C indicated that liquid phase GC was more efficient in displacing antibody binding reactivity than liquid phase C. The displacement effect of both liquid phase antigens was greatest against solid phase C. We conclude that anti-H1 autoantibodies are directed against an epitope located near the junction of the G- and C-domain which is exposed and not masked when H1 is bound to DNA.

HLA-A and -B alleles in cornea donors as risk factors for graft rejection.

We determined the human leucocyte antigen (HLA)-A, -B and -DR allele frequencies in recipients and donors of 115 cornea transplants, for recipients who developed graft rejection and those who did not. No difference in HLA allele frequencies of the recipients was found. The frequencies of the HLA-A26, -B35 and -B44 alleles in cornea donors were increased in recipients who developed graft failure. The detrimental effect on corneal graft survival of these alleles was significant (p < 0.001). No such effect was observed in renal transplantation. Corneal graft survival was similar when one or two A26, B35 or B44 alleles were present on the donor cornea. The negative effect was similar in magnitude to the previously reported negative effect of an HLA-B locus match between donor and recipient. When both a B-locus match and an A26, B35 or B44 allele were present, the negative effect on graft survival was twice as strong, indicating that different immune mechanisms are responsible for these phenomena.

Rebound effect of the allogenic T-cell response to donor and third-party lymphocytes after cyclosporine withdrawal in renal transplant recipients.

Mixed lymphocyte reaction (MLR) assays were performed serially over 24 months in 19 first cadaver renal transplant recipients. Immunosuppression consisted of cyclosporine, methylprednisolone and azathioprine. Cyclosporine was withdrawn at 6 months postoperatively. The MLR reactivity gradually decreased over the first 3 months following transplantation. However, there was a significant increase in MLR reactivity at 12 months postoperatively after the cyclosporine withdrawal. This rebound effect in MLR reactivity following cyclosporine withdrawal could account for the increased incidence of acute rejection episodes.

Lack of reactivity of sera from Theileria parva-infected and recovered cattle against cell membrane antigens of Theileria parva transformed cell lines.

Sera from Theileria parva infected, recovered and rechallenged cattle were tested in complement-dependent cytotoxicity, membrane immunofluorescence and antibody-dependent cellular cytotoxicity assays for the presence of antibodies against cell membrane antigens of T. parva transformed cell lines. In the complement-dependent antibody-mediated cytotoxicity assay, sera from lethally infected animals were negative. Some recovered cattle showed a positive reaction, but such reactions were also observed when an eland cell line infected with T. taurotragi, and bovine lymphoblastoid cells were used as targets. Reaction was less against Ig-negative peripheral blood lymphocytes. Evidence is presented that these reactions could be evoked by attachment of immune complexes to Fc-receptors. It is concluded that cattle exposed to T. parva infection do not develop antibodies against specific T. parva (or T. parva-induced) cell surface antigens.