J. Gabriel Michael

In vitro cross-allergenicity of major aeroallergenic pollens by the radioallergosorbent technique☆☆☆

Cross-reactivity between major classes of aeroallergenic pollens has been estimated by comparing the inhibitory effects of selected allergens upon the reaginic activity of other native and non-native varieties, as measured by the radioallergosorbent technique (RAST). Common allergenic determinants were demonstrated in indigenous and nonindigenous ragween species. Although patterns of inhibitory capacity were less uniform among grass pollens, endemic species tended to have more common allergenic properties than nonendemic species. Tree pollens exhibited the greatest degree of heterogeneity, confirming the previous view that these pollens tend to be less cross-reactive. Concomitant skin test threshold studies utilizing the same groups of pollens were in general agreement with in vitro results. Because, threshold skin testing was affected by a number of uncontrollable variables, however, the current modification of RAST in estimating cross-allergenicity was more accurate and reliable than data based upon cutaneous tests. It was concluded that reagin neutralization by the RAST method is the best currently available method of assessing cross-allergenic properties of pollens.

Immunologic Effects of Encapsulated Short Ragweed Extract: a Potent New Agent for Oral Immunotherapy

BACKGROUNDnOral allergen immunotherapy with conventional allergens has not been a useful mode of treatment because of the lack of potency of allergens when administered by this route.nnnOBJECTIVEnTo study the immunologic potency of short ragweed pollen extracts microencapsulated by a new technique administered orally to short ragweed pollen-sensitive humans and to establish the dose of oral microencapsulated short ragweed pollen extract required for these effects.nnnMETHODSnNine short ragweed pollen-sensitive patients were treated with a new oral agent for immunotherapy, microencapsulated short ragweed pollen extract, in an open study. The effectiveness of this treatment was determined by comparison to a group of nine matched short ragweed pollen-sensitive patients who received no treatment. Treated patients developed high titers of short ragweed-specific IgG and IgE antibodies and their expected seasonal increase in IgE antibodies was regulated. The dose of microencapsulated short ragweed pollen extract required to achieve these effects was only slightly higher than the dose of short ragweed pollen extract used in high dose subcutaneous immunotherapy. Furthermore, this dose was achieved in 7 weeks. There were no side effects other than mild gastrointestinal ones. The nine treated patients fared clinically better during the ragweed season than the untreated patients in this open study.nnnCONCLUSIONnThis study suggests that allergens microencapsulated by this new technique may make oral immunotherapy a practical mode of treatment.

Breaking of Oral Tolerance by an Encapsulated Antigen

Induction of oral tolerance is influenced by the form of antigen delivered. We showed that an intact soluble protein antigen or its enzymatic digest (antigenic fragments), when administered orally to mice, are both capable of inducing oral tolerance. However, when these two forms of antigen are administered directly into the ileum, the intact antigen becomes immunogenic, but antigenic fragments remain tolerogenic. We concluded that if the digestion of the antigen in vivo by the proteolytic enzymes of the gastrointestinal tract is prevented, orally administered antigen will be immunogenic. To test this concept, hen egg albumin (OVA) was encapsulated by a novel technology deveioped in our laboratory. This technology uses an acrylic, pH-sensitive polymer, resistant to dissolution at acidic pH (< 6.0), but dissolving at higher pH. Thus, encapsulated proteins are not affected by proteolytic enzymes of the stomach and are delivered intact to the small intestine where they interact with the gut-associated lymphoid tissue. Several antigens were encapsulated and administered orally to mice, rats, and guinea pigs. Also, in two FDA-approved studies, encapsulated allergens were given orally to humans (ragweed extract allergens to ragweed-sensitive individuals). These encapsulated antigens initiated a powerful immune response. Both primary and secondary responses were observed. These responses were characteristic of a Th2 cell dependent activation, inasmuch as IgG,, IgA, and IgE classes of antibodies predominated. IgGh and IgGzb classes of antibodies, which are Thl dependent, were not detected. To study the T-cell activation patterns of encapsulated OVA, the number of cytokine-secreting cells were enumerated in lymphoid organs by an ELISPOT assay. Mice fed with encapsulated OVA

Peptic fragments of bovine serum albumin bind antigen-specific T suppressor cells from orally tolerized mice

The antigenic structures capable of binding immunoregulatory T cells have been investigated. The functional properties (suppression or help) of BSA-specific T cells from primed or orally tolerized mice with capacity to adhere to bovine serum albumin or its peptic fragments were examined in reconstitution experiments in which splenic T-cell populations together with naive B cells were transferred into irradiated syngeneic recipients. Antigen-specific T suppressor cells isolated from mice tolerized to BSA adhered to peptic fragments of BSA as well as to the intact antigen. BSA-specific T helper cells adhered only to the intact antigen. Our data suggest that the preferential activation of T suppressor cells following administration of peptic fragments may be due to their ability to adhere to such fragments. These findings offer a novel approach of separation and identification of T suppressor cells and may be useful in further studies of immunosuppression.

Immunoregulation of the anti-bovine serum albumin response by polyclonal and monoclonal antibodies

Monoclonal or polyclonal antibodies directed toward determinants on limited structures of bovine serum albumin (BSA) (P505-582) were shown to regulate the entire anti-bovine serum albumin (BSA) immune response when passively administered to mice 24 hr prior to immunization. Regulation was observed as suppression of the humoral IgG immune response toward all BSA determinants except those on fragment P505-582. By Day 21 suppression of humoral response was most pronounced toward determinants present on the carboxy terminal end of the molecule (N 307-582). These observations demonstrate that monoclonal antibodies directed against a single determinant on a protein molecule have the capacity to regulate the immune response to a multiplicity of determinants present on the same protein. The data lend support to concepts of antibody-induced regulation by induction of suppressor cells or idiotype recognition.

Beta2‐Microglobulin in Human Tumors Heterografted into Athymic Mice1

Abstract. Beta2‐microglobulin (β2m) content of several human tumor lines implanted into athymic mice was investigated. The concentration of this protein was found to vary greatly from tumor to tumor. The growth rate of the tumors was inversely related to the amount of the extractable β2m. The fastest growing, undifferentiated tumors contained the least amount of β2m.