The effect of antigenic competition on various manifestations of humoral antibody formation and cellular immunity

A key to the backdoor into the castle: The clinical ramifications of immunoediting driven by antigenic competition

Over the last decade the field of cancer biology has gained considerable data on genomic heterogeneity. This situation creates challenges and possibly opportunities for cancer treatment. The evolution of the tumor at all stages also requires the growing malignancy to confront and avoid the immune system. What we describe here is the interaction of two immune phenomena that work together to change the characteristics of the tumor, i.e., antigenic competition and immune editing. These two systems are mutually functional and their interaction is capable of altering the characteristics of the tumor for protection and survival in an immune competent host as well as restricting the diversity of the tumor clones. Therefore, the final outcome of these interactions can also become the key to the backdoor into the castle. Through an additional immune manipulation, autologous tumor cell immunization, we can achieve prevention of disease recurrence after surgical resection and by analyzing induced human monoclonal antibodies to the neoantigens, gain in site into the restriction of diversity of the mutant clones. These findings may also open the door for a pathway to immune prevention of cancer.

The consequences of the intracellular retention of pathogen-derived T-cell-independent antigens on protein presentation to T cells

Intracellular pathogens can be considered as particulate antigens chemically composed of a complex mixture of T-cell-dependent antigens (TD) (peptides and proteins) and T-cell-independent antigens (TI) (glycolipids and complex polysaccharides). A large range of saccharides (from oligosaccharides to complex polysaccharides) derived from pathogenic microorganisms are being isolated and characterized. They are currently implicated in signaling systems and concomitant host-parasite relationships. However, there are not many structure-function relationships described for these pathogens. This is particularly true of polysaccharides. In this report we have reviewed the role of defined TI antigens in the processing and presentation of defined TD antigens to specific T cells by antigen-presenting cells (APC). We also considered the importance of some of the chemical characteristics shared by different carbohydrates implicated in the inhibition of antigen presentation. These findings are discussed in relation to the clear immunopathological consequences of long retention periods of complex carbohydrate molecules derived from intracellular parasites inside certain APC and the absence of antigen presentation impairment in physiological situations such as the removal of senescent or damaged red blood cells by splenic macrophages or intracellular accumulation of carbohydrates in colostrum and milk macrophages during lactation.

Virosomes as carriers for combined vaccines

Immunopotentiating reconstituted influenza virosomes (IRIV) are liposomes which carry the two glycoproteins of the influenza virus on their surface. A hepatitis A vaccine using IRIV as carrier has very good immunogenicity and is well tolerated. The objective of this study was to produce a fivefold combined vaccine against hepatitis A and B, diphtheria, tetanus and influenza A/B, and to show that in principle IRIVs can serve as carriers for multiple antigens which have good immunogenicity and are well tolerated. A total of four studies were carried out. Either the combined vaccine or the corresponding adequately tested alum-adsorbed single vaccines were tested for reactogenicity and immunogenicity in young adults. A hepatitis A and B combination on an IRIV base showed the same immunogenicity and toleration as the single vaccines. However, with the simultaneous coupling of all five vaccines on the same IRIV or the binding of Di-Te and HAV on different IRIVs there was a suppression of the humoral immune response against HAV (p = 0.03). The possibility that epitope-specific suppression had occurred could be ruled out. The suppression of the response against HAV could be circumvented by halving the quantity of Di-Te antigen in the combined vaccine so as to avoid antigenic competition. Surprisingly, the immunogenicity of Di-Te vaccination in the combination proved superior to that of a separate vaccination. All vaccinations were well tolerated.

Immunoregulation in fish II: intermolecular-induced suppression of antibody responses studied by haptenated antigens in atlantic salmon (Salmo salar L)

Here we report evidence for T cell dependent intermolecular-induced suppression of antibody responses in fish, using a panel of T cell dependent (TD) and T cell independent (TI) hapten-carrier antigens. Atlantic salmon were immunized intraperitoneally either with protein antigens: Limulus polyphemus hemocyanin (LPH), chicken gammaglobulin (CGG), A. salmonicida surface A-layer protein (ALPAsal) or lipopolysaccharide (LPS) antigens isolated from A. salmonicida and Escherichia coli. The various antigens were given as a mixture of the native and haptenated (4-hydroxy-3-iodo-5-nitrophenyl-acetic acid, NIP; 2,4,6-trinitrophenyl-acetic acid, TNP; fluorescein-5-iso-thiocyanate, FITC) forms. The salmon immune system responded to the antigen mixtures by eliciting high anti-hapten titers whereas the antibody titers against protein determinants were low (suppress 65-95%) as determined by ELISA. The suppression was induced between haptens (NIP and FITC) and between heterologous antigens (NIP-CGG and LPH) indicating that the mechanisms involved were non-specific. Moreover, suppression was induced by TD antigens only, indicating that the mechanism was T cell dependent. Injection of antigen mixtures containing variable amounts of the competing antigens showed that the kinetics of suppression was dose-ratio and dose dependent. In a time-course study it was found that the suppressed anti-LPH response was unchanged until native LPH was injected almost 2 years after the primary immunization, showing that permanent tolerance had not been induced. Sequential immunization showed that the antibody response was most sensitive to suppression during the initial 10 days after immunization. Moreover, the carrier antigen was also able to induce suppression of hapten epitopes, but only if the anti-carrier response was allowed to develop for 14 days before the hapten-carrier antigen was injected. This shows that AIS in fish is elicited as a result of the immune response to the dominant antigen, and can be induced against either antigens if the temporal order of administration is reversed. A possible model for AIS as a normal immunoregulatory process in fish is proposed and discussed.

Protective effect of a T-cell-dependent immunosuppressive, B-cell-mitogenic protein (F3'EP-Si, or P90) produced by Streptococcus intermedius

The role of a previously described bacterial protein (F3'EP-Si), now designated P90, in the survival of Streptococcus intermedius in the host was investigated, and the immunosuppressive and B-cell-mitogenic effects of this protein were further characterized. C57BL6 mice treated with P90 were about 50 times more susceptible to infection with this bacterium than untreated mice. One of seven splenocytes of C57BL/6 mice were activated by P90. Marked splenomegaly was observed in mice treated with P90, with increased numbers of splenic mononuclear cells and polyclonal immunoglobulin-secreting plaque-forming cells. Peak responses were seen on day 3 for immunoglobulin M (IgM) and on day 5 for IgG, with an isotypic pattern consisting predominantly of IgG2a and IgG2b. When mice were treated with P90 before being primed with sheep erythrocytes, polyclonal immunoglobulin synthesis was accompanied by an ephemeral stimulation of the specific immune response against sheep erythrocytes that was quickly replaced by a dramatic immunosuppression. In contrast, when mice were treated with P90 after being primed, the polyclonal activation was comparatively much less evident and there was no suppression of the specific immune response. Immunosuppression was considerably reduced in mice thymectomized as adults or depleted of CD8+ cells. Adoptive transfer experiments showed that B cells obtained from P90-treated mice were less able to respond to an antigenic challenge, even in the presence of normal T cells, and that T cells obtained from P90-treated mice could actively suppress the specific immune response of normal B cells.

Antigen induced modulation by shed lymphocyte membrane gangliosides

A unique regulatory mechanism has been proposed for ganglioside which functions to immune responses to temporarily restrain B lymphocytes of all specificities and at various levels of differentiation. Utilizing antigen competition protocols, experiments was designed to exploit and extend the antigen induction properties of this modulation. Spleen cell cultures were prepared from TNP-BGG primed mice. In vitro stimulation of the cultures with ovalbumin (OVA) followed 24 hours later by addition of TNP-BGG resulted in only one weak TNP hemolytic plaque responses when compared to control cultures which did not receive OVA. OVA induced competitive effects were absorbed by anti-Thy-1 or anti-ganglioside. Glycolipids could be extracted from the culture media supernatants of experimental and control groups as a ganglioside fraction containing Thy-1 determinants. These molecules, when formulated into liposomes, produced the same modulatory effect as that of media from the competitive culture group. These results support and extend the proposal that glycolipids released by antigen stimulated T cells provide unrestricted modulation of B cells to prevent overload during T cell maturation. This regulatory mechanism prevents direct antigen binding and prepares B cell receptivity for further stimuli which orchestrate their terminal differentiation into plasma cells.

Antigenic competition in the induction of contact sensitivity in mice

Antigenic competition in contact sensitivity was found to occur between DNFB and PCl and also between some other pairs of non-cross reacting sensitizers. When mice were painted with DNFB 0-7 days before the sensitization with PCl, the responsiveness to PCl was suppressed completely, whereas when DNFB was painted after sensitization with PCl, the responsiveness to PCl was affected. The prior application of DNFB resulted in the reduction of DNA synthesis in the draining lymph nodes of PCl-sensitization. This indicated that the suppression by painting with DNFB was not attributable to the inactivation of PCl-specific effector T cells which had already been generated by the sensitization with PCl, but to the inhibition of the generation of PCl-specific effector T cells. The antigenic competition occurred even when two contact sensitizing agents were applied to different lymphoid regions of mice. The suppressive effect of DNFB on the PCl-sensitization was observed also in the mice which had been made tolerant to DNFB. These results seem to imply that the antigenic competition in the present experimental system is the phenomenon which may not be mediated by effector T cells but rather by other cells, possibly suppressor cells.

Antigenic competition between heterologous erythrocytes in mice. Immunological and histological studies exploring mechanisms of the antigenic competition

To explore the mechanisms of antigenic competition, immunological and histological studies were made on mice using non-crossreacting heterologous erythrocyte antigens, i.e. sheep (SRBC), horse (HRBC) and chicken (CRBC) erythrocytes. Deficiency in the competition-inducing capacity of CRBC which we demonstrated in a previous paper was corroborated by the results that under any experimental conditions examined CRBC were unable to induce the competition. Of interest in the studies was that when anti-HRBC antibody responses of mice pre-injected with SRBC, i.e. competing antigen, were examined on day 2 and day 4 of HRBC-immunization, the day-2 response was revealed to be significantly enhanced, whereas the day-4-response was markedly suppressed as a result of the antigenic competition. By contrast, pre-injection with CRBC, i.e. non-competing antigen, did not affect at all either day-2 or day-4 anti-HRBC response of mice. Histological features of the spleens of mice either being prepared for antigenic competition or undergoing competitively suppressed antibody response were characterized by prominent regeneration of hyperplastic germinal centres, involving appearance of numerous tingible bodies and distinct collars of small lymphocytes which suggested massive proliferation and degeneration of lymphocytes. The spleens of mice in the immunological state indifferent to antigenic competition were characterized by huge lymphatic follicles which contained very few tingible bodies and were circumscribed by a markedly attenuated zone of small lymphocytes. From all these results, we suggest that massive proliferation and differentiation of T lymphocytes, probably toward regulatory (suppressor) T cells, could account for a mechanism of antigenic competition, and that deficient competition-inducing capacity of CRBC should be ascribed to weakness of their capacity in activation of the regulatory T lymphocytes.

Characteristics of immunological memory in mice. II. Resistance of nonrecirculating memory cells to antigen-mediated suppression of the secondary antibody response

Mice were primed and subsequently challenged at various times with subcutaneous injections of sheep erythrocytes, and some characteristics of the secondary responses in the draining brachial and axillary lymph nodes were investigated. It was found that the secondary response within primed nodes was resistant to immunological preemption, a competition-like phenomenon which severely depresses primary responses. Since it was also shown that circulating memory cells could be inhibited by preempting injections of antigen, it was concluded that the resistance of primed nodes to preemption was due to the presence within them of a nonrecirculating subpopulation of memory cells. The size of this population was dependent both on the amount of priming antigen and the time after priming. The observation that the response given by these cells remained unaffected by doses of antigen which could depress a primary response does not favor the view that suppression of immune responses by preemption or antigenic competition is due to a factor which acts directly and indiscriminately on all immunologically competent cells.

Competition between skin-sensitizing chemicals in the mouse

The skin contact sensitivity responses to picryl chloride in CBA mice can be reduced by prior sensitization with oxazolone. Initial experiments showed this reduction to be significant when the interval between skin paintings was 7 days. In further experiments to study the time course of this effect, the depression was found to be maximal when the interval between skin paintings was between 3 and 7 days.

Prior painting with a non-immunogenic chemical irritant, oil of turpentine, did not depress responses to picryl chloride.

The relation of this phenomenon to antigenic competition in antibody production is discussed.

Increased production of plaque-forming cells in mouse lymph nodes following regional injection of a second antigen

An analysis was made of the antibody response in the spleen and lymph nodes of mice to erythrocyte antigens injected under conditions which have been reported to cause antigenic competition. In the spleen, injection of a different erythrocyte antigen 2–4 days before the injection of a test antigen had little or no effect on the total number of cells or the number of plaque-forming cells (PFC) to the test antigen. Examination of the antibody response in opposite lymph nodes of a mouse made possible a comparison between two different conditions of antigen exposure within the same individual. In the lymph nodes, preceding the injection of the test antigen by an injection of a different erythrocyte antigen 2–4 days earlier led not to a decrease, but, on the contrary, to an increase in the number of plaque-forming cells to the test antigen. A similar increase in the number of plaque-forming cells per lymph node was observed for each of two test antigens, when these had been mixed and injected into the forefeet 24 hours after the injection of a different erythrocyte antigen.

Studies on antigenic competition. II. Evidence for effect at level of antigen 'processing'

Antigenic competition between two haptenic determinants was studied. It was shown that antigenic competition was greater if a 1- or 2-week interval is imposed between injection of the two antigens. Preimmunization with one antigen or with the carrier protein to which one hapten is coupled will decrease the effect of antigenic competition on the antibody response to that antigen or hapten and bring about a greater degree of depression of the antibody response to the second haptenic determinant. Finally, antigenic competition does not occur if the two antigens are injected so as to drain into different groups of regional lymph nodes. This is true even if a 3- or 7-day time interval is imposed between injection of the two antigens.

The results are interpreted as suggesting that competition occurs at the level of the antigen `processing' or `localizing' step in the immune response.

In vivo requirement for a radiation-resistant cells in the immune response to sheep erythrocytes

Experiments have been done to establish whether the radiation-resistant or A cell has a specific function in the initiation of an immune response in mice to sheep erythrocytes (SRBC). All previous demonstrations using accessory (A) cells have involved in vitro assays and are possibly explainable as tissue culture artifacts. If A cells are essential, it should be possible to demonstrate their requirement in vivo. Therefore we first established such conditions. Two methods were found for creating an A-cell deficiency in vivo: (a) A cells disappear gradually from the spleens of irradiated mice, presumably by migration since A-cell function was shown not to be decreased by irradiation. If 3 days elapse between irradiation and transplantation of mixtures of bone marrow and thymus cells (which provide B and T but few A cells), the usual synergistic response does not occur. Addition of large numbers of freshly irradiated spleen cells to the mixture of bone marrow and thymus completely restores the immune response. (b) Injection of 10(10) horse erythrocytes into mice suppresses A-cell activity in these mice 24 hr later; a much reduced response to SRBC is obtained when they are given at this time. The response can be partially restored if irradiated spleen cells are given with the SRBC. This observation formed the basis for a quantitative in vivo assay for A cells in which the magnitude of restoration by various suspensions of irradiated cells was used to estimate the A-cell activity of that suspension. A quantitative in vitro assay for A cells was also developed. It was essential for this assay that the total cell number, B-cell number, and T-cell number be kept constant and that only the number of A cells be allowed to vary. Only under these conditions was the response a linear function of the number of A cells added. If the in vivo and in vitro assays are detecting the same class of radiation-resistant cells, the physical properties of the cells active in each assay should be identical. Spleen cells were separated on the basis of both density and sedimentation velocity. Fractions from both separation methods were tested for their content of A cells using both the in vivo and in vitro assays. The density and sedimentation profiles of A cells were similar in both assays. The demonstration that a radiation-resistant cell is required in vivo and that this cell has properties identical to the radiation-resistant cell required in vitro indicates that this cell (the A cell) is directly involved in the initiation of an immune response to erythrocyte antigens.

Studies on antigenic competition. I. Antigenic competition between the Fc and Fab fragments of rabbit IgG in mice

In the antibody response to rabbit IgG in BALB/c mice, antigenic competition has been demonstrated between Fc and Fab'. Similar competition was found when a mixture of Fc and Fab' was used as antigen. In both cases the presence of Fc suppressed the antibody response to Fab'. Competition was demonstrable only in the primary antibody response. The effect on competition of varying the routes and the time course of administration of the antigens was investigated.

A cellular deficit in the reconstitutive capacity of immune populations of lymphoid cells demonstrable in studies of delayed hypersensitivity in mice. Evidence for thymus-bone marrow cell synergism

A cell-transfer system was employed in the present work to investigate several characteristics of the capacity of immune and normal lymphoid cells to transfer the delayed response to methylated human serum albumin in lethally irradiated syngeneic recipients. Spleen cells derived from donor mice immunized with goose erythrocytes were far less effective in transferring responsiveness when compared with equal numbers of normal cells. Statistical analyses indicated a frequency of 1 reactive cell or cell unit in 1.3 x 10(7) normal cells and in 6.2 x 10(7) immune cells. These findings provided confirmatory evidence that antigen-induced suppression (antigenic competition) employing sequential administration of two non-cross-reacting antigens is due to relative deficits of immunocompetent cells generated by lymphoproliferation in lymphoid tissues secondary to immunization with the initial antigen. The cellular deficit in the immune population was shown to be resident in a thymus cell population, which restored the number of responders to a level equivalent to the normal population. The thymic cell was akin to the antigen-reactive cell. The cell limiting the degree of response, that is the effector cell for both normal and immune cell populations, was of bone marrow origin. Both populations of cells were shown to act in synergy to reconstitute the delayed response to the antigen.

Antigenic Competition Between and Endotoxic Adjuvant and a Protein Antigen

Antigenic competition between bovine gamma globulin (BGG) and endotoxin from a smooth strain (S-ET) and a rough (R-ET) heptoseless mutant strain of Salmonella minnesota was studied in mice. Both endotoxins acted as adjuvants for enhancing the antibody response to BGG. However, other work showed that the R-ET had minimal antigenicity, and it was used as a control for the competition studies. Antigenic competition between BGG and endotoxin as expressed by a suppression of the antibody response to BGG could not be demonstrated when varying adjuvant doses of S-ET or R-ET were injected simultaneously with a small constant dose of BGG into normal mice. However, mice presensitized with S-ET several weeks before immunization with the S-ET and BGG combination produced anti-BGG levels which were four to eightfold lower than in normal mice. Nearly complete suppression of the anti-BGG response could be obtained in presensitized mice by reducing the BGG dose 10-fold or by increasing the adjuvant dose of endotoxin. Mice pretreated with R-ET and challenged with BGG plus S-ET or R-ET showed no depression of the anti-BGG response. These and other experiments confirmed the immunological basis of the competitive effect.

Antigen competition: a paradox

Immunization of mice with pig erythrocytes caused impairment of the antibody response to subsequent immunization with sheep erythrocytes, a phenomenon called "antigen competition." Paradoxically, spleen cells from mice previously injected with pig erythrocytes produced an increased response when immunized in vitro with sheep erythrocytes. Augmentation of the in vitro response is due to an increase in one of the interacting cell types. "Antigen competition" is not due to competition for cells. Cell transfer experiments provided evidence that "antigen competition" observed in animals is the result of a humoral factor, presumably antibody, present in the animal but eliminated during preparation of cells for culture.

Quantitation of the antigenicity and immunogenicity of purified foot-and-mouth disease virus vaccine for swine and steers

The antigenicity and immunogenicity of a purified preparation of foot-and-mouth disease virus [type A(12), strain 119 (FMDV A-119)] inactivated with 6.0 mmN-acetylethylenimine at 37 C were compared in swine and steers. Three antigen doses were tested, 640, 160, and 40 ng. In accordance with findings for guinea pigs, as previously determined by dose-response curves, as little as fourfold changes in antigen in the region of the minimum effective dose produced marked differences in the serological and immune responses of swine. The minimum effective dose of antigen for antibody formation in swine and guinea pigs, as determined by mouse median protective dose (PD(50)) values, was 160 ng. The minimum immunogenic dose for swine was also 160 ng. The vaccinated swine were challenged with either FMDV A-119 or with heterologous subtype A(24) strain Cruzeiro or type A strain A-CANEFA-1. Those immunized with 640 ng of antigen were about equally immune to the three challenge viruses; most swine having a mouse PD(50) value of 2.0 or greater were immune regardless of which strain was used for challenge. In steers, the smallest dose tested, 40 ng, was satisfactory in eliciting circulating antibodies and immunity. Physical and biological tests indicated that the antigen used in the vaccine is stable for at least 9 months at 4 C.

Antigen competition: antigens compete for a cell occurring with limited frequency

Experimentally altered ability of transferred spleen cells to generate hemolytic plaque-forming cells provided evidence that antigens compete for a type of multipotential cell that contributes to the formation of immunologically competent units. De'ay of exposure of transferred spleen cells to antigen provided results which suggest that different types of cells interact to form competent, antigen-reactive units even in the absence of antigen.

Studies on antigenic competition

Antigenic competition was studied in a haptenic system. It was found that: (a) The extent of competition is greater when larger doses of antigen are employed. (b) Antigenic competition appears to be independent of the carrier molecule. (c) The affinity of the antibody produced in antigenic competition is approximately equal to the affinity of antibody formed by animals immunized with only one antigen. (d) Antigenic competition only occurs when both antigens are injected so as to drain into the same regional lymph nodes. The results suggest that antigenic competition occurs locally at the site of antigen stimulation and is not mediated by a circulating factor, by tolerance induction, or by suppression due to synthesis of cross-reacting antibodies.