Immunity to onchocerciasis: cells from putatively immune individuals produce enhanced levels of interleukin-5, gamma interferon, and granulocyte-macrophage colony-stimulating factor in response to Onchocerca volvulus larval and male worm antigens

Antigen-specific interleukin-5 (IL-5), gamma interferon (IFN-gamma), and granulocyte-macrophage colony-stimulating factor (GM-CSF) responses in individuals living in an area of hyperendemicity for onchocerciasis in Cameroon were examined. The responses against antigens prepared from Onchocerca volvulus third-stage larvae (L3), molting L3 (mL3), and crude extract from adult males (M-OvAg) were compared to the responses against antigens from adult female worms and skin microfilariae. Cytokine responses for the putatively immune individuals (PI) and the infected individuals (INF) were compared. A differential cytokine profile of IL-5 (Th2 phenotype) and IFN-gamma (Th1 phenotype) was found in these individuals in response to the antigens. In both the PI and the INF, Th2 responses against all the antigens tested were dominant. However, in the PI group as a whole, there was an enhanced Th2 response against the larval antigens and the adult male and adult female antigens, and a Th1 response in a subgroup of the PI (27 to 54.5%) against L3, mL3, and M-OvAg antigens was present. While the PI produced significantly higher levels of GM-CSF against L3, mL3, and M-OvAg antigens than the INF, there was no difference in the GM-CSF responses of the groups against the other antigens. The present study indicated that, in comparison to the INF, the PI have distinct larva-specific and adult male-specific cytokine responses, thus supporting the premise that immunological studies of the PI would lead to the identification of immune mechanisms and the target genes that play a role in protective immunity.

Frequency of B cells expressing germ-line gamma 1 transcripts upon IL-4 induction

Murine B cells when activated with LPS and IL-4 have been shown to secrete IgG1 and IgE with corresponding H chain gene rearrangements. Using this system it has been previously demonstrated that transcription of gamma 1 and epsilon C region genes in their germ-line configuration occurs before switch recombination. Here, for the first time, the frequencies of B cells expressing germ-line gamma 1 transcripts are analyzed using in situ hybridization methodology. The results indicate that the combination of LPS and IL-4 induces a relatively low frequency of cells (5-12%) to express germ-line gamma 1 transcripts. Germ-line gamma 1 transcript-expressing cells were first detected on day 1 of culture with LPS and IL-4 and reached a maximum by days 3 to 5. The B cells that expressed germ-line gamma 1 transcripts appeared to be activated based on size and morphology. The frequency of B cells expressing germ-line gamma 1 transcripts approximated the frequency of C gamma 1+ plasma cells that appeared later in the cultures. These data may suggest a correlation between germ-line Ig transcript expression and the frequency of B cell precursors committed to the expression of a particular isotype.

Frequency of B cells expressing germ-line gamma 1 transcripts upon IL-4 induction

Murine B cells when activated with LPS and IL-4 have been shown to secrete IgG1 and IgE with corresponding H chain gene rearrangements. Using this system it has been previously demonstrated that transcription of gamma 1 and epsilon C region genes in their germ-line configuration occurs before switch recombination. Here, for the first time, the frequencies of B cells expressing germ-line gamma 1 transcripts are analyzed using in situ hybridization methodology. The results indicate that the combination of LPS and IL-4 induces a relatively low frequency of cells (5-12%) to express germ-line gamma 1 transcripts. Germ-line gamma 1 transcript-expressing cells were first detected on day 1 of culture with LPS and IL-4 and reached a maximum by days 3 to 5. The B cells that expressed germ-line gamma 1 transcripts appeared to be activated based on size and morphology. The frequency of B cells expressing germ-line gamma 1 transcripts approximated the frequency of C gamma 1+ plasma cells that appeared later in the cultures. These data may suggest a correlation between germ-line Ig transcript expression and the frequency of B cell precursors committed to the expression of a particular isotype.

Characterization of an unusual cell type (CD4+ CD3-) expanded by helminth infection and related to the parasite stress response

Mice infected with the parasite Mesocestoides corti develop hypergammaglobulinemia, hepatomegaly, and splenomegaly. The immune response to M. corti infection is directed, in part, at molecules secreted by the organism. Two of these molecules have been shown to be hsp70 and hsp60 homologues. In this study it was found that incubation of splenocytes from infected animals with M. corti-secreted molecules or the isolated M. corti hsp70 results in the expansion of an unusual cell type with the morphology of large granular lymphocytes. The cell lines express Thy-1, CD4 (low), and CD45RB but lack TCR alpha beta, TCR gamma delta, CD3, CD8, and slg. The lack of a TCR suggested NK cells, but no cytolytic activity could be detected. In addition, the cell lines constitutively produce IL-6 and can be induced to express IL-2, but not IL-4, IL-5, or IFN-gamma. Given the phenotype of these cells, it is possible that they represent T lineage precursors or some type of effector cells. Notably, CD3- CD4+ cells appear to be expanded in the spleens and livers of M. corti-infected animals, suggesting an important role in infection. Moreover, the selective growth of this cell type with M. corti hsp70 suggests that the outgrowth and in vivo expansion of these cells may be related to the stress response of the parasite.

Characterization of an unusual cell type (CD4+ CD3-) expanded by helminth infection and related to the parasite stress response

Mice infected with the parasite Mesocestoides corti develop hypergammaglobulinemia, hepatomegaly, and splenomegaly. The immune response to M. corti infection is directed, in part, at molecules secreted by the organism. Two of these molecules have been shown to be hsp70 and hsp60 homologues. In this study it was found that incubation of splenocytes from infected animals with M. corti-secreted molecules or the isolated M. corti hsp70 results in the expansion of an unusual cell type with the morphology of large granular lymphocytes. The cell lines express Thy-1, CD4 (low), and CD45RB but lack TCR alpha beta, TCR gamma delta, CD3, CD8, and slg. The lack of a TCR suggested NK cells, but no cytolytic activity could be detected. In addition, the cell lines constitutively produce IL-6 and can be induced to express IL-2, but not IL-4, IL-5, or IFN-gamma. Given the phenotype of these cells, it is possible that they represent T lineage precursors or some type of effector cells. Notably, CD3- CD4+ cells appear to be expanded in the spleens and livers of M. corti-infected animals, suggesting an important role in infection. Moreover, the selective growth of this cell type with M. corti hsp70 suggests that the outgrowth and in vivo expansion of these cells may be related to the stress response of the parasite.

Serine proteinase of Renibacterium salmoninarum digests a major autologous extracellular and cell-surface protein

Renibacterium salmoninarum is a pathogen of salmonid fish that produces large amounts of extracellular protein (ECP) during growth. A proteolytic activity present in ECP at elevated temperatures digested the majority of the proteins in ECP. This digestion was also associated with the loss of ECP immunosuppressive function. In vitro activity of the proteinase in ECP was temperature dependent: it was not detected in an 18-h digest at 4 and 17 degrees C but became readily apparent at 37 degrees C. Proteinase activity was detected at bacterial physiological temperatures (17 degrees C) in reactions incubated for several days. Under these conditions, digestion of partially purified p57, a major constituent of ECP and a major cell-surface protein, yielded a spectrum of breakdown products similar in molecular weight and antigenicity to those in ECP. This pattern of digestion suggests that most of the immunologically related constituents of ECP are p57 and its breakdown products. The proteolytic activity was sensitive to phenylmethylsulfonyl fluoride, methanol, and ethanol and to 10-min incubation at temperatures above 65 degrees C. Electrophoretic analysis of the proteinase on polyacrylamide gels containing proteinase substrates indicated the native form to be 100 kDa or greater. The enzyme was active against selected unrelated substrates only when coincubated with a denaturant (0.1% lauryl sulfate) and (or) a reducing agent (20 mM dithiothreitol).