Source antigens

Species origin tests, used to determine whether the specimen is human or from another source, are immunological in nature. Host animals, usually rabbits, are injected with protein from another species. The animal creates antibodies to the unknown material. Semm from the host animal, containing species (human, bovine, equine, canine, etc) specific antibodies, is tested against a dilute solution of blood (antigens) collected as evidence. A positive reaction is determined by a visible band where the antibodies and antigens come into contact. 

Two types of antibody libraries can be constructed, immune or non-immune. Immune libraries are constructed by immunizing the animal of interest with an antigen(s). In the case of humans, the source can be volunteers with the disease or condition under study (Persson et al., 1991). Human antibodies have also been obtained from severe combined immunodeficiency mice populated with human peripheral blood... 

As mentioned above, yS T cells are numerous in the gut and can produce cytokines in the absence of conventionally presented antigen (Kaufmann, 1996). These cells have been shown to produce IL-4 or IFN-y (Ferrick el al., 1995) and are potentially an important source of these cytokines in the intestinal microenvironment following nematode infection. Supporting this suggestion, IL-4 mRNA has been found in y8 T cells from the caecum of resistant mice immediately following T. muris infection (Lukaszewski and R.K. Grencis, unpublished observations). 

In some cases, the preparation of a fluorescently labeled antibody is not even necessary. Particularly, if indirect methods are used to detect antibody binding to antigen, then preparing a fluorescently labeled primary antibody is not needed. Instead, the selection from a commercial source of a labeled secondary antibody having specificity for the species and class of primary antibody to be used is all that is required. However, if the primary antibody needs to be labeled and it is not manufactured commercially, then a custom labeling procedure will have to be done. 

FIGURE 11.12 TSA method using the conventional ABC method, together with pretreatment procedures and optimal antigen retrieval. Source www.hmds.org.uk/ histology.html... 

In order to compare the specific activity of plant-derived C5-1 to that of the hybridoma-derived antibody, the antigen-binding capacity of antibodies produced in each system was assayed by enzyme-linked immunosorbent assay (ELISA). As shown in Table 1.2, antibodies from both sources demonstrated similar binding characteristics against human IgGs [8]. Furthermore, the stability of alfalfa-derived C5-1 in the blood stream of Balb/c mice was comparable to that of the hybridoma-derived IgG [8]. 

Proteins such as antibodies, enzymes, hormones and vaccine antigens can be used to prevent, diagnose and treat a range of diseases. Such molecules are therefore of paramount importance in health and medicine. Historically, many of these proteins have been isolated from human or animal sources. However, the low quantities present in such source material coupled with safety risks and high purification costs have limited the availability of protein therapeutics and vaccines for many types of disease. 

Non-immune libraries are produced in a similar fashion, but using B-lymphocytes fromnon-im-munized donors as a source of antibody genes. This approach becomes necessary if initial immunization with the antigen of interest is not possible (e.g. due to ethical considerations). Although such... 

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