Morphological, serological and molecular analyses of anthracnose-causing agent on banana fruit

Two species of the genus Colletotrichum, C. musae and C. gloeosporoides, occur as infecting species of banana. The study focused on examining the etiology of anthracnose on banana fruits sold on the domestic market. An isolate was obtained from a diseased banana fruit on PDA medium, forming a white colony with intensive and uniformed growth. It was not possible to identify the isolated fungus based on its morphological characteristics. Positive serological reaction in an ELISA test with monoclonal antibodies for C. acutatum indicated an antigen site for the used monoclonal antibodies. Positive reaction when C. gloeosporioides-specific primers were applied indicated a similarity in the ITS sequence of the fungus and the examined isolate from banana fruit. Although there are no available data in literature that C. gloeosporioides-specific CgInt primer can be used for amplification of the phylogenetically related C. musae, our results do not exclude that the isolate could be C. musae. The host plant, symptoms observed and colony characteristics of the fungus isolated from the banana fruit mostly correspond to C. musae. Based on morphological, antigen and gentic characteristics, the isolate from banana was determined as Colletotrichum sp., while species identification of the anthracnose-causing agent on banana requires additional analysis.

Effect of antigen site and complement receptor status on the rate of cleavage of C3c antigen from red cell bound C3b

C3b was bound to human red cells when serum complement was activated by addition of antibodies directed against different red cell antigens, and the rate of cleavage to C3dg was determined by assay for loss of bound C3c antigens using radiolabeled monoclonal anti-C3c. When C3b was bound by antibodies to antigens on branched-chain glycoproteins, cleavage to C3dg occurred more rapidly than when C3b was bound by antibodies to antigens closer to the red cell lipid bilayer. The rate of cleavage to C3dg also correlated directly with the number of complement receptors (CR1) per red cell, reflecting their role as cofactors in the cleavage of iC3b by factor I. Thus, the life span of C3b/iC3b on human red cells, which may be important for determining the rate and mechanism of clearance of C3-coated red cells, appears to depend on the CR1 status of the red cells and the characteristics of the antigen sites around which complement is bound.

Effect of antigen site and complement receptor status on the rate of cleavage of C3c antigen from red cell bound C3b

C3b was bound to human red cells when serum complement was activated by addition of antibodies directed against different red cell antigens, and the rate of cleavage to C3dg was determined by assay for loss of bound C3c antigens using radiolabeled monoclonal anti-C3c. When C3b was bound by antibodies to antigens on branched-chain glycoproteins, cleavage to C3dg occurred more rapidly than when C3b was bound by antibodies to antigens closer to the red cell lipid bilayer. The rate of cleavage to C3dg also correlated directly with the number of complement receptors (CR1) per red cell, reflecting their role as cofactors in the cleavage of iC3b by factor I. Thus, the life span of C3b/iC3b on human red cells, which may be important for determining the rate and mechanism of clearance of C3-coated red cells, appears to depend on the CR1 status of the red cells and the characteristics of the antigen sites around which complement is bound.

Quantitative immunoferritin microscopy of Fya, Fyb, Jka, U, and Dib antigen site numbers on human red cells

The Fya, Fyb, Jka, U, and Dib antigen site numbers and ultrastructural distribution patterns on the human erythrocyte membrane were determined using quantitative immunoferritin microscopy. For homozygous antigen- positive red cells, the average number of determinants per red cell was about 14,000 for Jka, 17,000 for Fya and Fyb, 19,000 for Dib, and 23,000 for the U antigen, assuming that the equilibrium binding observed represented 80% saturation of the accessible antigen sites. The site numbers for this group of antigens were less than that for the Rh antigens, but considerably more than the Kell and Cellano antigens. The technique used was capable of demonstrating a twofold difference in antigen density between heterozygous and homozygous Fy (a+) red cells. More than 85% of the Fya and Fyb antigen sites were lost following pretreatment of the red cells with papain, consistent with the serologic lability of the Fy antigens following proteolysis. The ferritin distribution observed following conjugate staining of antibody- sensitized ghost membranes was similar for all five antigens studied and showed a random, clustered ferritin pattern. Although the quantitative estimates are valid, the remarkable similarity in antigen distribution pattern for this diverse group of antigens, as well as other considerations, suggest that the findings with ghose membranes probably do not reflect faithfully the antigen arrangement on the intact red cell membrane.