Enhancement and inhibition of immunological mechanisms by immunosuppressive agents. I. Dose effect on priming and generation of memory to a bacterial antigen

A new experimental system is described which allows the study of the effect of immunosuppressors upon the priming and generation of memory to an antigen from Escherichia coli. A single dose of bacterial beta-D-galactosidase without adjuvant injected into C57B1/6J mice primes and elicits memory but not antibodies. Thus by administering immunosuppressors near the priming injection, one can examine whether primary antibody formation is enhanced and whether priming generation of memory is enhanced or inhibited. We found that X-rays, cyclophosphamide and oxisuran (2-[(methylsulfinyl)acetyl]pyridine) either enhance or inhibit the elicitation of memory, depending on dosage, although they do not alter primary antibody unresponsiveness. The data show two main features: (a) immunosuppressors can enhance immunization; and (b) generation of memory can be improved without increasing antibody levels. The former finding draws attention to the role that immunosuppressors might play in the breaching of tolerance to self-antigens which share determinants with microbes, while the latter observation shows that antibody synthesis and elicitation of memory can follow independent pathways.

Long-term antibody synthesis in vitro- IV. Independent segregation of antibodies directed to different determinants of an antigen molecule in its native configuration

Independent segregation of antibody populations directed to different portions of E. coli beta-d-galactosidase occurs during the immune response against the enzyme. Anti-enzyme antibodies able to interact and activate a naturally occurring ligand, the mutant-defective enzyme AMEF (Antibody Mediated Enzyme Factor), do not parallel anti-enzyme antibodies which are measured by a coprecipitation assay involving precipitation of the wild-type molecule. Dissociation of the two antibody populations is best achieved in microcultures sustaining long-lasting responses. Similarly, anti-NIP (4-hydroxy-3-iodo-5-nitrophenylacetic acid) antibodies could be elicited without concomitant synthesis of anti-carrier antibodies by short-term challenge in vitro of ovalbumin-NIP-primed lymph nodes with a heterologous conjugate in which the hapten NIP was coupled to a carrier known to be non-immunogenic under the conditions of challenge. The potential applications of these findings are indicated, namely: large-scale production of monospecific antibodies in vitro; and the possibility of studying the regulatory role of antibodies directed towards on portion of the immunogenic molecule on the response to other regions of the same molecule.

Nasopharyngeal carcinoma. IX. Antibodies to EBNA and correlation with response to other ebv antigens in chinese patients

Ninety-five sera from Chinese NPC patients in different stages of the disease, 38 sera from Chinese patients with other cancers, and 50 normal Chinese sera, were titrated for EBNA, VCA, EA and complement-fixing (CF/S) EBV-specific antibodies. The geometric mean (GMT) EBNA antibody titre of patients with NPC at stage I was found to be four times higher than that of normal individuals and increased in parallel with clinical deterioration. Antibody titres against EBNA did not correlate with either VCA or EA antibodies but, in general, correlated with CF/S antibodies. EA antibodies correlated relatively well with VCA antibodies and discriminated better than EBNA titre between NPC at stage I and controls.

Long-lasting in vitro immune response to a distinct antigenic determinant of a bacterial protein. Cyclic changes of antibody titer and affinity

Long-lasting (60 days or more) antibody responses in vitro by rabbit lymph node fragments to a distinct determinant of Escherichia coli beta-D-galactosidase were obtained by supplementing culture medium with fetal calf and horse serum. Antibodies released in the supernatant were removed every 3rd to 5th day together with the spent medium, without pooling to minimize intermixing of molecules synthesized far apart in time. Antibody titer, association constant, and heterogeneity index were measured in medium samples collected throughout the response in order to draw profiles of their changes under conditions whereby a limited number of clones synthesize antibodies in a closed system without connection to antigen depots, central lymphoid organs, and circulating cell and antibody pools. It was found that antibody affinity changes cyclically and that such cycles may be repeated. Cycles are composed of an ascendant limb with a gradual increase in affinity and a parallel diminution of heterogeneity. A descendant limb follows with the opposite modifications. High affinity antibodies predominate at the peak of the cycles, whereas low affinity molecules take over at the end of the cycles until the next ascendant limb begins; these persist after the last cycle has waned.

In vitro antibody response to a distinct antigenic determinant of Escherichia coli beta-D-galactosidase. Effect of antigen dosage and co-cultivation of lymph node fragments on peak titres and duration of antibody synthesis

The anti-β-D-galactosidase activating antibody response in lymph node fragment cultures was investigated in an attempt to understand the mechanism determining the magnitude of an immune response towards a natural hapten, which occurs only once in each antigen molecule, under in vitro conditions that preserve the histology of the responding tissue. Fragments were individually challenged for defined time periods, and washed; cultures with one and two fragments were then set up. Co-cultivation of fragments produced titres higher than predicted from results in single fragment cultures. This happened even when the latter cultures produced low titres because of excessive antigen dosages. Co-cultivation of fragments also improved the duration of the antibody response. These effects appeared to correlate with the number of memory cells present in the fragments at the beginning of the cultures. These observations, together with data obtained by manipulating different doses and times of antigen exposure suggest that collaboration between cells and determinants with different specificities may occur, not only in the initial induction, but also in the sequential stimulation of antibody-forming clones. It is postulated that the co-operative mechanism shown to act in the initiation of the antibody response by cell suspensions toward polyvalent artificial conjugates may also operate when intact lymphoid tissue is reached by a single bacterial determinant in its natural molecular configuration

An immunoenzymatic system to study in vitro immune responses. Synthesis of antibodies directed toward different -D-galactosidase determinants in lymph node fragment cultures

A system for studying in vitro the antibody response against a single determinant and to all the determinants of a macromolecule (β-D-Galactosidase of Escherichia coli) is described. It consists of culturing fragments of rabbit lymph nodes (either preimmunized in vivo or not) and exposing them to antigen in vitro. Antibodies secreted into the culture during several days, and up to 3 months in the secondary response, were titrated for: (a) one-hit activation AMEF, the cross-reacting material produced by a point mutant Lac^-E. coli; and (b) precipitation of wild type enzyme. Titrations of activating and binding antibodies are very sensitive owing to the amplification potential inherent in the enzymatic assays, which allows several antibody measurements on minute samples. In addition antigen decay in vitro was followed and correlated with the antibody response, showing faster disappearance when the latter took place. Time-course studies of the in vitro antibody response demonstrated that precipitating titres are higher and last longer than activating antibody titres. Repeated in vitro challenges showed decay of the memory potential of in vivo primed lymph nodes, as well as the possibility of inducing an immune response in vitro using non-primed lymph nodes. The results underline the amenability of the present system to the study of in vitro primary and secondary immune responses toward restricted portions of a macromolecule.

Maturation of the immkune response in vitro. Focal fluctuation and changes in affinity of anti-beta-D-galactosidase activating antibody

We have cultivated lymph node microfragments from beta-D-galactosidase (Escherichia coli) primed rabbits and have measured their secondary response directed towards the whole molecule (precipitating antibodies) and to a single determinant (activating antibodies) of the antigen. By decreasing the size of the fragments to 10(5) cells, we began to observe heterogeneity among identical cultures in terms of positivity of response, antibody specificity, and titers. The affinity of "early" activating antibodies was inversely proportional to the dose of challenge. While no maturation was seen in low and excessive challenge, in all cultures receiving intermediate doses the association constant was raised several orders of magnitude within periods of 20 days. The relevance of these data to the mechanism of affinity selection of antigen-sensitive cells is discussed.