Studies on the Product of Antigenic Recognition III.

Abstract

The product of antigenic recognition (PAR) is an antigen-antibody complex with granulotactic activity. The following results support his conclusion. PAR generated by cell-bound or shed T-cell RS or the recognizing structure of T alloantisera and alloantigen can be destroyed by heating at 56 °C for 30 min, because of inactivation of a heat-labile component supplied by alloantigen. Recognizing partners of these complexes are heat-stable. They form PAR anew when alloantigen is added or upon confrontation with anti-RS serum. They are also capable of inducing anti-RS sera. PAR preparations composed of these recognizing structures and antibodies to them are heat-inactivated at much higher temperatures, because both partners of the complex are relatively heat-stable. Heat-labile PAR complexes (recognizing structures and alloantigen) pass anti-mouse immunoglobulin immunosorbent, but are retained specifically by alloantiserum (via alloantigen of the complex) or by anti-RS serum (via RS of the complex) bound to the column.

Similarity of Idiotypic Determinants of T‐ and B‐Lymphocyte Receptors for Alloantigens

“…This contrasts sharply with the IgG-associated principle of T alloantisera which, within minutes and exactly to dilutions determined in indirect PAR tests as their anti-H-2 titers, solubilized alloantigens to form PAR (Ramseier & Lindenmami 1977a). Furthermore, as mentioned, T-cell receptors (cellbound or shed) also solubilized alloantigens and mimicked an anti-H-2 titer (Ramseier & Lindenmann 1977a).…”

“…Absorption of sera with B cells might well have neutralized the anti-B RS activity, but this was not tested. Absorption, however, did not inactivate the B alloantibody activity as shown by the normal anti-H-2 titer which resulted from binding to and shielding of alloantigen C57BL/6 present on Fi target spleen cells (Ramseier & Lindenmann 1977a), most probably because the alloantiserum was itself B RS (C57BL/6). Neutralization of antisera induced with and directed against T-cell receptor idiotypes by spontaneously shed B-cell receptors is shown in Tables VI and VII.…”

“…When normal CBA or C57BLy6 serum in dilutions of 1:2 to 1:8 was incubated for 4 hours at 37°C with (C57BL/6 X CBA)Fi target cells, there was no PAR formation. Similarly, B alloantisera failed to form PAR with alloantigens present on corresponding Fi target cells when tested from 1:8 to well above their indirect PAR test titers (Ramseier & Lindenmann 1977a) and, finally, shed B-cell receptors also failed to form PAR with alloantigens (Ramseier, unpublished). The conclusion was, therefore, that receptors present in normal sera or in B-cell supemates generated anti-H-2 titers by fixing to H-2 antigens without solubilizing them.…”

“…For T material, a titer endpoint is generated by a dilution incapable of alloantigen solubilization; for B material, by that dilution incapable of alloantigen shielding. Thus, in combination with PAR formation in so-called direct PAR assays (Ramseier & Lindenmann 1977a), a clear functional distinction between T-and B-cell receptors can be obtained. Another important functional discrimination is the ability to induce anti-T cell receptor sera, which immanipulated T-, but not B-material, has (Ramseier 1975a).…”

“…The test system used to determine activity and titers of antisera was the PAR assay. The test procedure is fully described (Ramseier 1974a(Ramseier , 1975a and data on its mechanism have been given (Ramseier & Lindenmann 1977a). Only so-called indirect PAR tests have been employed here: a) to determine activity and titers of anti-T cell receptor sera, 2 X 10^ unfractionated parental spleen cells or T cells prepared from them were treated with serum dilutions for 15 min at 37°C in a moist atmosphere of 95 % air to 5 % CO2, washed, and about 10* of such treated lymphocytes were confronted with about 10^ untreated Fi spleen cells carrying the appropriate alloantigen hi 5 ml of HBSS for periods allowing maximal PAR formation; b) to measure alloantiserum activity and titers, serum dilutions were used to treat 2 X 10^ Fj spleen cells and about 10* washed lymphocytes were confronted under the same conditions as above with about 10* untreated parental cells, carrying the appropriate alloreceptors.…”