Comparative genomic study of arachnid immune systems indicates loss of beta-1,3-glucanase-related proteins and the immune deficiency pathway.

Analyses of arthropod genomes have shown that the genes in the different innate humoral immune responses are conserved. These genes encode proteins that are involved in immune signalling pathways that recognize pathogens and activate immune responses. These immune responses include phagocytosis, encapsulation of the pathogen and production of effector molecules for pathogen elimination. So far, most studies have focused on insects leaving other major arthropod groups largely unexplored. Here, we annotate the immune-related genes of six arachnid genomes and present evidence for a conserved pattern of some immune genes, but also evolutionary changes in the arachnid immune system. Specifically, our results suggest that the family of recognition molecules of beta-1,3-glucanase-related proteins (ßGRPs) and the genes from the immune deficiency (IMD) signalling pathway have been lost in a common ancestor of arachnids. These findings are consistent with previous work suggesting that the humoral immune effector proteins are constitutively produced in arachnids in contrast to insects, where these have to be induced. Further functional studies are needed to verify this. We further show that the full haemolymph clotting cascade found in the horseshoe crab is retrieved in most arachnid genomes. Tetranychus lacks at least one major component, although it is possible that this cascade could still function through recruitment of a different protein. The gel-forming protein in horseshoe crabs, coagulogen, was not recovered in any of the arachnid genomes; however, it is possible that the arachnid clot consists of a related protein, spätzle, that is present in all of the genomes.

Analysis of the phenotypic effects of B chromosomes in a natural population of Metagagrella tenuipes (Arachnida: Opiliones).

Phenotypic effects of B chromosomes in a natural population of Metagagrella tenuipes (Arachnida: Opiliones) were studied. Mean number of Bs per individual in the population studied was 6.0, and remained stable during two successive summers of 1997 and 1998. In contrast to the number of B chromosomes, ratios between individuals possessing odd and those possessing even numbers of Bs changed during both collection seasons: the proportion of harvestmen with an even number of Bs decreased from June-July to October-November. A possible reason for this may be a difference in susceptibility to parasites between B-odd and B-even harvestmen. In the group of B-even individuals the percentage of infected harvestmen in the June-July samples was much higher compared to the B-odd group. In addition, the infection rate in the B-even group decreased more sharply than among B-odd harvestmen. In the group of B-even harvestmen infection was associated with reduced body size, whereas no such association was found among B-odd harvestmen. In the group of B-even individuals there was a U-shaped relationship between number of Bs and the probability of being infected by parasites, and an inverted-U-shaped relationship between body size and number of Bs. No such associations were found in the group of B-odd harvestmen. Seasonal selection is suggested to be a main factor contributing to the B-chromosome polymorphism in M. tenuipes.

Parasitic dermatoses that cause pruritus in horses.

Insect hypersensitivity is the most common cause of equine pruritus. It is a seasonal, highly pruritic dermatosis that is caused by the salivary antigens of biting insects. The most common insects are discussed in terms of the area of the horse affected, clinical signs, therapy, and preventative strategies.

Galactans and anti-galactans from invertebrates.

Antibody-like substances with anti-carbohydrate specificities directed against different structures of galactans have been detected in several invertebrates.

Differentiation of human leukemic from normal lymphocytes by Limulus serum agglutination.

Human peripheral chronic lymphocytic leukemic lymphocytes and a line (B411-4) of cultured human B cells are agglutinated by Limulus serum to a significantly higher titer and score than peripheral normal human lymphocytes or a line (MOLT-4-F) of cultured human T cells.

Sialyl residues in hepatitis B antigen: their role in determining the life span of the antigen in serum and in eliciting an immunological response.

Hepatitis B surface antigen was adsorbed to insolubilized sialic acid-specific haemagglutinin isolated from the haemolymph of Limulus polyphemus. Treatment of the antigen with Vibrio cholerae neuraminidase (EC 3.2.1.18) resulted in the release of sialic acid and in an increase of the isoelectric point from pH 4-35 (for subtype ad) or 4-9 (for subtype ay) to pH 5-45. Treated, but not untreated, antigen incorporated [14-C]-sialic acid when incubated at 37 degrees C with sialyl transferase (EC 2.4.99.1) and cytidine-5'-monophosphate-[14-C]-sialic acid. The major portion of [14-C]-sialic acid was linked to a glycoprotein with an apparent mol. wt. of 26 x 10-a. De-sialylated antigen had a drastically reduced in vivo life span in rabbit plasma and elicited a higher humoral antibody response than intact antigen (subtype ad). Antigen-stimulated proliferation of lymphocytes, measured 3 months after immunization, was observed only with cells from rabbits injected with neuraminidase-treated antigen.

Specific effect of neuraminidase on blastogenic response of sensitized lymphocytes.

The blastogenic response of sensitized lymphocytes from guinea-pigs to 'de novo' antigens (KLH, HCH and PPD) was ehhanced by BCN treatment in twenty-one of twenty-three instances. In contrast, no effect of VCN on nonsensitized guinea-pig lymphocyte response to these antigens, or to mumps antigen, was noted in any of thirty-four instances, These findings indicate that the enhancement effect of VCN is specific for sensitized lymphocytes. Heating VCN at 100 degrees for 10 minutes completely abolished the enhancement effect on the lymphocyte response. VCN treatment did not change the kinetics of antigen-induced blastogenesis. The increased lymphocyte response could probably be related to unmasking of the antigen receptor sites of the cells, resulting in increased antigen uptake, following the VCN treatment.

Investigations on the specificity of the Limulus test for the detection of endotoxin.

Lysates obtained from amoebocytes of Limulus polyphemus, the horseshoe crab, showed gel formation after the addition of bacterial endotoxin. In contrast to living gram-negative bacteria, viable gram-positive microorganisms did not cause gelation of lysate. Nevertheless, peptidoglycan isolated from the cell walls of various gram-positive organisms did induce the reaction. However, the activity of peptidoglycan was 1,000 to 400,000 times less than that of Escherichia coli lipopolysaccharide. After exposure to lysozyme, peptidoglycan no longer gelled amoebocyte lysate, therefore apparently excluding endotoxin contamination. Gelation of amoebocyte lysate by endotoxin or peptidoglycan was inhibited by different concentrations of sodium polystyrolsulfonate. Whereas these studies confirm the specificity of the Limulus test for bacterial endotoxins, they also indicate that other substances of bacterial origin should be investigated for their ability to gel amoebocyte lysate.