Restriction fragment length polymorphisms of horse class II MHC genes observed using various human alpha-and beta-chain cDNA probes

Genomic DNA isolated from 20 horses was digested with up to six restriction endonucleases and subjected to southern blot hybridization analysis using various human class II alpha- and beta-chain cDNA probes. A high degree of restriction fragment length polymorphism (RFLP) was found for the DQ alpha, DP beta, DQ beta and DR beta probes, about 20 polymorphic bands being detected for each. DR alpha showed 2-4 polymorphic bands, whereas no evidence for DP alpha-like genes was found. A number of correlations of RFLPs with individual alloantisera were apparent.     

Effect of increased CO2 concentration and temperature on the phyllosphere mycoflora of winter wheat flag leaves during ripening

The impact of elevated carbon dioxide (CO₂, 600/700 μmol mol^-1) and temperature (+ 4°C) on phyllosphere fungi colonising flag leaves of mini crops of winter wheat cv. Mercia between anthesis and harvest was determined in a computer-controlled environment facility in 1993 and 1994. In both years the total fungal populations (cm² leaf) were found to have increased due to exposure to either elevated CO₂ and elevated CO₂+ temperature treatments. This was mainly due to significant increases in populations of Cladosporium spp. (C. cladosporioides and C. herbarum) on the flag leaves during ripening. Other phyllosphere component species such as white and pink yeasts were not markedly affected by treatments. The range of fungal species found in such controlled environment chambers was narrower than that commonly found on flag leaves of field grown crops. Common and important colonisers of leaves and ripening ears such as Aureobasidium pullulans, Epicoccum nigrum and Fusarium spp. were seldom isolated.     

Serological and genetic study of the ELA W21 specificity

Investigations on the W21 specificity showed that this antigen is expressed on lymphocytes and platelets but not on erythrocytes. The molecule carrying the antigen W21 moves in the cell membrane independently from ELA locus A and B encoded antigens, as observed in 'lysostripping'. The W21 specificity occurs with very different gene frequencies in various breeds. In informative families it segregates together with defined gene products of the MHC region. The data suggest strongly that the W21 specificity belongs to the ELA system as a class I gene product, but is governed by a separate locus than the known locus A and locus B allelic series.     

Loading of Peptide on to MHC Molecule is Not Essential for Clearance of Cryptosporidium pawum

ABSTRACT: Transgenic and knockout mice usefully model the mechanisms that result in the clearance of Cryptosporidium parvum from the gut. CD4⁺ cells, cells expressing MHC class II, and CD154/CD40 interactions are essential. Unexpectedly, AND RAG-/- and DO11.10 RAG-/- mice with single specificities of T cells successfully clear Cryptosporidium infection. Clearance is accompanied by activation of CD4⁺ cells in the MLN. The ability of T cells bearing receptors for apparently irrelevant and non-cross reactive antigens to activate and to clear infection is surprising. The requirement for class II MHC expression for Cryptosporidium clearance raises the alternative possibilities that (a) class II MHC is required to present a peptide that is loaded as a consequence of infection or (b) that the cytokine environment engendered by a Cryptosporidium infection allows affinity for self MHC to activate nahe T cells. In order to test the hypothesis that peptide loading is necessary, we used ApEα-/-Ii-/- mice that express a hybrid IA-IE MHC molecule. They also carry a transgene that makes an Ea peptide while disruption of their invariant chain blocks the loading of a foreign peptide on to their MHC class II molecules. After oral gavage, the course of infection was followed by ELISA. CD4⁺ cells in the MLN of these mice were activated to express CD69 and the infection was cleared. We conclude that the loading of a Cryptosporidium or other infection-dependent peptide onto the MHC class II molecules of APCs is not necessary for clearance of Cryptosporidium. Instead the TcR affinity for self-MHC must suffice for T cell activation in the cytokine environment resulting from infection