Detection of B-lymphocytes secreting antibodies to Dermatophagoides antigens

Construction and diversity analysis of a murine IgE phage surface display library

To make further investigation of the IgE antibody repertoire in Trichosanthin (TCS) allergic responses, a murine IgE phage surface display library was constructed (3.0 x 10(5) independent clones). We first constructed the V epsilon cDNA library (4.6 x 10(5) independent clones) and V kappa cDNA library (3.0 x 10(5) independent clones). Then, the V epsilon and V kappa gene segments were amplified from both libraries by PCR respectively, and assembled into Fab fragment by SOE PCR. The phage library containing Fabs was thus constructed. The diversity of V epsilon from this library was analyzed and proved. Fab clones with high specificity to TCS have been screened out.

A simplification of the enzyme-linked immunospot technique. Increased sensitivity for cells secreting IgG antibodies to Haemophilus influenzae type b capsular polysaccharide

A simplified enzyme-linked immunospot (ELISPOT) technique is described for the detection of cells secreting antibodies to tetanus toxoid (TT), diphtheria toxoid (DT) or Haemophilus influenzae type b capsular polysaccharide (PRP). By combining the cell suspension with the enzyme-linked secondary antibodies in one incubation, the second incubation and washing procedure could be omitted from the original technique. The simplified assay had the same sensitivity for anti-TT and anti-DT spot-forming cells as the ordinary ELISPOT assay. The IgG anti-PRP spots were, however, improved both in quality and in quantity (median: 40% more spots), while the detection of IgM and IgA anti-PRP spot-forming cells was the same in the two techniques. This simplified technique can probably also be used to save time in other antigen systems and should be considered when designing ELISPOT assays for the detection of polysaccharide-specific antibody-secreting cells.

The allergen specific B-cell response during immunotherapy

The paper examines the allergen specific B-cell response in peripheral blood from patients undergoing immunotherapy with house dust mite extract. The 12 patients were part of a double blind placebo controlled study, and they were treated with either Dermatophagoides pteronyssinus (n = 4), Dermatophagoides farinae extract (n = 3) (Alutard SQ, ALK, Denmark) or placebo (n = 5). Blood was taken every fortnight on day seven after hyposensitization and tested for IgM, IgG, IgA and IgE antibody secreting cells (AbSC) to D. pteronyssinus and D. farinae allergens and for the total number of immunoglobulin secreting cells (IgSC). The data showed a maximum of approximately 120 Der f I+II specific AbSC/10(6) mononuclear cells (MNC). A comparison of specific AbSC to the major allergens of the two house dust mites demonstrated that there was no measurable species specificity in the B-cell response that could be correlated to immunotherapy with either of the two extracts. The specific IgM, IgG, and IgA response to Der f I+II was examined in the placebo (39 measurements) and the actively treated (56 measurements) groups, and the results demonstrated a significant rise in specific IgM and IgA AbSC following immunotherapy. The number of specific IgG AbSC did not change. There was a mean of less than one specific IgE AbSC/10(6) MNC, and no detectable change following the treatment. It is speculated that immunotherapy to inhalant allergens causes the induction of specific IgA AbSC. It would then be these partly differentiated plasma cells that are detected on their way to the bronchial or gut mucosa to exert their protective function mediated by allergen specific secretory IgA.

Isolation and amplification of human IgE Fd encoding mRNA from human peripheral blood lymphocytes

In order to establish the feasibility of applying recombinatorial library technologies to investigate human in vivo IgE responses, and as a pre-requisite of recombinatorial library construction, we have attempted to determine workable peripheral blood sample volumes required for isolation of mRNA for polymerase chain reaction (PCR) amplification of human IgE Fd encoding sequences. Cells secreting chimeric human IgE monoclonal antibody specific for the hapten NIP were used to establish the conditions for specific amplification of C epsilon 1 domain and Fd encoding sequences, as determined by Southern hybridisation. Amplification of C epsilon 1 domain sequences could be achieved using as few as ten cultured cells as the source of RNA. Specific IgE+ B cell enrichment using immuno-magnetic particles prior to RNA extraction was, however, required to obtain amplification of IgE C epsilon 1 and Fd fragments from lymphocytes prepared from 40 ml human peripheral blood. IgG1+ B cell enrichment from similar samples was not required for detectable amplification of human C gamma 1 cDNA sequences. However, this procedure improved amplification efficiency. Optimisation of methods to separate specific B cell populations, or specific RNA/cDNA sequences, will facilitate in vitro generation of human IgE Fab fragments from peripheral blood.