Ontogeny of B-lymphocyte function. I. Restricted heterogeneity of the antibody response of B lymphocytes from neonatal and fetal mice.

The ontogeny of the ability of B lymphocytes to produce an antihapten response which is heterogeneous with respect to affinity for the antigenic determinant was studied in a cell transfer system. The heterogeneity of affinity of the immune response of lethally irradiated mice reconstituted with syngeneic, adult thymus cells and fetal or neonatal tissues as a source of B lymphocytes was studied. It was found that B cells from 17 day fetal liver or neonatal liver are highly restricted with respect to heterogeneity of affinity as compared with adult spleen or bone marrow. The B-cell population achieves an adult character with respect to heterogeneity of affinity by 2 wk of age. The peripheral lymphoid tissues (spleen) appear to mature in this respect more rapidly than do central lymphoid tissues (bone marrow). Spleens from 10-day old donors behave in an adult, heterogeneous manner while bone marrow from the same donors exhibit a marked restriction in heterogeneity of affinity. Germfree mice produce an immune response which is indistinguishable from conventionally reared adult animals with respect to heterogeneity of affinity. The earlier appearance of the ability to transfer a heterogeneous immune response in spleen as compared with bone marrow suggests that the increasing heterogeneity of the B-lymphocyte population which occurs between birth and 2 wk of age is the result of a differentiation event and not of a somatic mutation or recombination event.

Ontogeny of B-lymphocyte function. II. Ability of endotoxin to increase the heterogeneity of affinity of the immune response of B lymphocytes from fetal mice.

The ontogeny of the functional capacity of B lymphocytes to generate a heterogeneous response to a haptenic determinant was studied by cell transfer techniques in LAF1 mice. Fetal liver, as a source of B lymphocytes, was transferred into adult, syngeneic, irradiated animals. All recipients received excess adult thymus cells so that T-cell activity did not limit the response and were immunized with DNP-BGG. The heterogeneity of avidity of their anti-DNP PFC response was assayed by hapten inhibition of plaque formation. Animals reconstituted with B lymphocytes from fetal donors produced a response that is highly restricted with respect to heterogeneity of affinity. Transfer studies using multiple fetal donors or mixtures of adult and neonatal cells for reconstitution suggest that the restriction in heterogeneity is not the consequence of suppressor T-lymphocyte activity. With animals reconstituted with B cells from day 16 or older fetal donors, injection of LPS together with antigen converted the response to a heterogeneous "adult-type" response. With animals reconstituted with B lymphocytes from day 14 fetal liver DxSO4, but not LPS, could convert the response to a highly heterogeneous one. Animals reconstituted with day 14 or 16 fetal liver as source of B lymphocytes were capable of producing a heterogeneous secondary response despite the fact that their primary response was of restricted heterogeneity. This implies the selection of high affinity B-memory cells, in the absence of high affinity PFC during the primary response with fetal B lymphocytes. Animals reconstituted with day 14 or 16 fetal liver produce only direct PFC, while animals reconstituted with day 18 fetal liver produce both direct and indirect PFC. Three differentiation events have therefore been defined in the functional development of B lymphocytes: (a) between day 14 and day 16 of fetal life they acquire responsiveness to LPS; (B) BETWEEN DAY 16 AND 18 OF FETAL DEVELOPMENT THEY ACQUire the capacity to produce indirect PFC; (C) between day 7 and 10 after birth they acquire the capacity to give a heterogeneous response after normal immunization. In addition, it was shown that LAF1 mice already have all of the information required to produce an "adult-type" heterogeneous anti-DNP response at day 14 of fetal life.

Carrier function in anti-hapten immune responses. II. Specific properties of carrier cells capable of enhancing anti-hapten antibody responses.

Transfer of live lymphoid cells from BGG-immunized strain 2 guinea pigs into syngeneic animals primed with DNP-OVA prepares the recipients for a markedly enhanced secondary anti-DNP antibody response upon challenge with DNP-BGG. This phenomenon has been demonstrated when the recipients were challenged 1 day after cell transfer, but it was considerably more striking when an interval of 6 days was allowed between transfer of cells and challenge with antigen. As demonstrated in the preceding paper (6), BGG preimmunization enhanced anti-DNP antibody responses to challenge with DNP-BGG. An analysis of the characteristics of substances to which preimmunization was effective in enhancing subsequent anti-hapten responses was made. It was shown that preimmunization of strain 13 guinea pigs with a copolymer of glutamic acid and lysine (GL), to which these animals are genetically unable to accord an immune response, failed to prepare them for an enhanced anti-DNP response to DNP-GL. Tolerance to BGG specifically abrogated the capacity of subsequent BGG immunization to prepare DNP-OVA primed rabbits for an enhanced anti-DNP response to DNP-BGG. Sensitization of animals to haptens by preimmunization with hapten-protein conjugates failed to prepare them for enhanced primary or secondary antibody responses to other determinants associated with that hapten on a different carrier. These studies indicate that the enhancing effect of carrier preimmunization reflects a cooperative interaction between lymphoid cells specific for carrier and cells specialized for haptenic determinants. Furthermore, the capacity of a substance to behave as a carrier requires more than its possession of a variety of antigenic determinants.

Carrier function in anti-hapten immune responses. I. Enhancement of primary and secondary anti-hapten antibody responses by carrier preimmunization.

Preimmunization of either guinea pigs or rabbits to bovine gamma globulin (BGG) prepares the animals for markedly enhanced antibody responses to 2,4-dinitrophenyl-BGG (DNP-BGG). This phenomenon is observed both in the primary anti-DNP antibody response to DNP-BGG and in the secondary anti-DNP antibody response to DNP-BGG in animals primed with DNP-ovalbumin (DNP-OVA). The BGG preimmunization is most effective if the antigen is administered as a complete Freund's adjuvant emulsion; in rabbits, a dose of 1 microg of BGG is more effective than a dose of 50 microg, whereas the reverse is true in guinea pigs. Transfusion of homologous anti-BGG sera fails to replace active immunization with BGG in the preparation of animals for these enhanced anti-DNP antibody responses. Both the immunoglobulin class and the average association constant for epsilon-DNP-L-lysine of the anti-DNP antibody produced in these enhanced responses is determined by the mode and time of immunization with haptenic conjugates and is not appreciably influenced by the nature of the carrier preimmunization. These studies indicate that the carrier specificity of hapten-specific anamnestic antibody responses is largely due to the interaction of two independent cell associated recognition units, one specialized for carrier and the other specific for haptenic determinants.

Carrier function in anti-hapten antibody responses. 3. Stimulation of antibody synthesis and facilitation of hapten-specific secondary antibody responses by graft-versus-host reactions.

The studies reported here demonstrate that immunocompetent lymphoid cells from allogeneic donor guinea pigs stimulate the synthesis of anti-DNP and anti-OVA antibodies by recipients previously primed with DNP-OVA. This allogeneic effect occurs spontaneously in the absence of any further anti-genic challenge. Furthermore, the transfer of allogeneic cells prepares DNP-OVA-primed recipients for a striking secondary anti-DNP response to DNP-BGG; this occurs in equal degree whether or not the cells are derived from BGG-primed donors. We suggest that the allogeneic cells function by virtue of a specific immunologic attack of grafted cells on host cells. This conclusion is made on the basis of the following evidence: (a) The failure of observing the phenomenon with L(2)C leukemia cells and irradiated strain 2 lymph node and spleen cells which, although capable of initiating a host-versus-graft response, are incapable of mediating graft-versus-host reactions; and (b) the inability of (strain 2 x strain 13) F(1) hybrids to mediate the allogeneic effect in strain 13 recipients. The analysis of this phenomenon may offer a key to the delineation of mechanisms involved in the activation of precursors of antibody-forming cells.

Immunological studies of aging. II. Loss of IgG and high avidity plaque-forming cells and increased suppressor cell activity in aging mice.

The magnitude and heterogeneity of the immune response to dinitrophenylated bovine gamma globulin was measured in aged and young mice at a cellular level using an inhibition of plaque-forming cell assay. The primary and secondary responses of 24-mo-old mice were markedly depressed in magnitude and restricted in avidity for the DNP determinant when compared to 2-mo-old animals. Bacterial lipopolysaccharide given at the time of immunization increased the restriction in heterogeneity seen in 12- and 24-mo-old mice. Indirect PFCs were more severely depressed than direct PFCs in 24-mo-old mice. Syngeneic, lethally irradiated, 2-mo-old mice reconstituted with aged spleen cells exhibit the depressed and restricted response to DNP-BGG seen in old mice. When 10(8) young thymus cells were given together with old spleen cells the heterogeneity of the response was increased. When 2-mo- and 24-mo-old spleen cells were transferred together into young recipients the magnitude of the response to the young spleen cells markedly reduced. Thus, there appears to be a loss of thymic-helper cells and an increase in suppressor activity in aged animals.

Production of auto-anti-idiotypic antibody during the normal immune response to TNP-Ficoll. II. Hapten-reversible inhibition of anti-TNP plaque-forming cells by immune serum as an assay for auto-anti-idiotypic antibody.

Sera taken from AKR/J mice 7 d after the intravenous injection of 2,4,6-trinitrophenyl-lys-Ficoll (TNP-F) caused a specific inhibition of anti- trinitrophenol (TNP) plaque-forming cells (PFC) in vitro. This inhibition was reversed by the incorporation of 10(-8)-10(-7) M 2,4,6-trinitrophenyl- epsilon-amino-n-caproic acid (TNP-EACA) into the agar during the PFC assay. The factor responsible for the hapten-reversible PFC inhibition was removed from serum by passage through an anti-immunoglobulin column or through a 2,4,-dinitrophenyl-human-serum-albumin-bromoacetylcellulose plus anti-TNP- antibody column, but not by DNP-HSA-BAC alone. It was concluded that this immunoglobulin-like substance, lacking anti-TNP activity but reacting with anti-TNP antibody of AKR/J origin, was most likely an auto-anti-idiotypie antibody that had been produced during the normal course of the response of AKR/J mice to TNP-F. Pools of anti-idiotypic-antibody-containing antisera inhibited anti-TNP plaque formation to varying degrees when tested on d-4 PFC from different mice of the same inbred strain, suggesting a variability in idiotype expression. 4 d after transfer of immune (7 d after 10 mug TNP-F, administered intravenously) AKR/J spleen cells plus 10 mug TNP-F into syngeneic mice, the number of PFC detectable in the recipients' spleens could be markedly augmented by the inclusion of TNP-EACA in the agar during the PFC assay. Incubation of spleen cells containing such hapten-augmentable PFC with TNP- EACA yielded a factor in the supernate that caused a specific, in vitro, hapten-reversible inhibition of anti-TNP PFC. Studies with immunoadsorbents indicated that this PFC-inhibiting factor was antigenically immunoglobulin- like, lacked anti-TNP-antibody activity, but reacted with anti-TNP antibody of AKR/J origin. The results are consistent with the view that this PFC inhibitor is auto-anti-idiotypic antibody that is involved in the normal regulation of the immune response. It is proposed that hapten-reversible inhibition of plaque formation can be employed as an assay for anti-idiotypic antibody and the conditions for such an assay are described. It is further proposed that the detection of hapten-augmentable PFC suggests the presence of auto-anti-idiotypic antibody.

Production of auto-anti-idiotypic antibody during the normal immune response to TNP-ficoll. I. Occurrence in AKR/J and BALB/c mice of hapten-augmentable, anti-TNP plaque-forming cells and their accelerated appearance in recipients of immune spleen cells.

Attempts were made to elucidate the cause of the downward regulation of the splenic plaque-forming cell (PFC) response in AKR/J and BALB/c mice between days 4 and 7 after a single intravenous injection of 2,4,6,trinitrophenyl- lys-Ficoll(TNP-F). AKR/J spleen cells, taken 7 d after injection of TNP-F, were transferred, together with TNP-F, into normal AKR/J mice. The day-3 or - 4 PFC response of the recipients was much lower than that of recipients of normal cells. However, the suppression was only apparent because the presence of 10(-8)-10(-7) M 2,4,6-trinitrophenyl-epsilon-amino-n-caproic acid (TNP- EACA) (or 10(-7)-10(-6) M 2,4,-dinitrophenyl-epsilon-amino-n-caproic acid) in the PFC assay caused a dramatic increase in observed PFC, averaging 298 percent on day 3 and 122 percent on day 4. Recipients of normal cells showed no such hapten-augmentable PFC. T-depleted immune spleen cells did not cause any apparent suppression of the response to TNP-F, but hapten-augmentable PFC in recipient spleens were again prevalent. Suppression of the PFC response, as well as hapten-augmentable PFC, were seen after transfer of immune serum. It was postulated that hapten augmentation of PFC was caused by displacement of auto-anti-idiotypic antibody from the surface of blocked antibody- synthesizing cells. Further studies showed that such hapten-augmentable PFC occurred in the spleens of a large percentage of both AKR/J and BALB/c mice examined after day 4 of the primary response to TNP-F. Thus, it was hypothesized that the downward regulation of the magnitude and, possibly, also of the heterogeneity of the splenic-PFC response was due to an auto-antibody response to one or more major idiotypes of the anti-TNP response.

Production of auto-anti-idiotypic antibody during the normal immune response to TNP-ficoll. III. Absence in nu/nu mice: evidence for T-cell dependence of the anti-idiotypic-antibody response.

Although athymic mice make an excellent immune response to the thymus-independent antigen trinitrophenyl-lys-Ficoll (TNP-F), nude mice of AKR/J and BALB/c strains lack the anti-idiotypic response that occurs in euthymic mice of both of these strains within the first 1--2 wk after injection of more TNP-F. Anti-idiotypic antibody-blocked (hapten-augmentable) anti-TNP splenic plaque-forming cells (PFC) do not occur at any time and serum anti-idiotypic antibody is absent in both congenitally athymic mice, and thymectomized, irradiated, bone marrow-reconstituted mice. Nevertheless, nu/nu mice do have PFC which can be inhibited by exposure to anti-idiotypic antibody produced in +/+ mice. As a consequence of the failure to produce anti-idiotypic antibodies, the anti-TNP PFC response is athymic as compared to euthymic mice is of greater magnitude, declines less precipitously, and shows an increase rather than a decrease in affinity between days 4 and 7 after antigen injection. It is concluded that the anti-idiotypic antibody response is thymus dependent and that athymic mice lack a helper cell required for the induction of anti-idiotypic antibodies.

Bone marrow function. I. Peripheral T cells are responsible for the increased auto-antiidiotype response of older mice.

After immunization with trinitrophenyl (TNP)-Ficoll, mice produced both anti-TNP antibodies and auto-anti-idiotype (auto-anti-Id) antibodies specific for the anti-TNP antibody. Older animals produced more auto-anti-Id than did young animals. When mice were exposed to a normally lethal dose of irradiation while their bone marrow (BM) was partially shielded, they survived and slowly (6 wk) regained immune function, as indicated by the number of nucleated cells in their spleen and the in vitro primary plaque-forming cell (PFC) response of their spleen cells to TNP-treated aminoethylated polyacrylamide beads. Recovery is presumably the result of repopulation of the peripheral lymphoid system by cells originating in the BM. By enzyme-linked immunosorbent assay (ELISA), and by hapten-augmentable PFC assay, we show that, after recovery from irradiation with their BM shielded, old animals produce low auto-anti-Id responses, like those of young animals. The transfer of splenic T cells into mice irradiated with their BM shielded provided evidence that the magnitude of the auto-anti-Id response is controlled by the peripheral T cells. Thus, mice that received splenic T cells from aged donors produced high levels of auto-anti-Id while those that received splenic T cells from young donors produce low levels of auto-anti-Id.

Production of auto-antiidiotypic antibody during the normal immune response. VII. Analysis of the cellular basis for the increased auto-antiidiotype antibody production by aged mice.

We have previously shown that old mice produce more hapten-augmentable plaque-forming cells (PFC) than do young animals, suggesting a greater auto-antiidiotype antibody (auto anti-Id) component in their immune response. In the present studies this is confirmed serologically. The marked auto-anti-Id response of aged mice can be transferred to lethally irradiated young recipients with spleen but not bone marrow cells from old donors, suggesting that it is an intrinsic property of their peripheral B cell population and that the distribution of Id arising from the bone marrow of old and young mice is similar. In contrast with young mice the auto-anti-Id response of old animals is relatively T cell-independent and old donors do not show an increase in their ability to transfer an auto-anti-Id response after priming with TNP-F. These observations suggest that old mice behave as if already primed for auto-anti-Id production. Irradiated mice reconstituted with bone marrow cells from either young or old donors together with splenic T cells from old donors generate a relatively large auto-anti-Id response, whereas mice reconstituted with bone marrow from either young or old donors together with splenic T cells from young donors produce few hapten-augmentable PFC. It is suggested that differences in Id expression and auto-anti-Id production are the consequences of the interaction of Id (and anti-Id) arising from the marrow with anti-Id (and Id) present in the peripheral T cell population which serves as a repository of information about shifts in Id distribution, resulting from lifelong interactions with environmental and self-antigens.

Radioresistance of cooperative function of carrier-specific lymphocytes in antihapten antibody responses.

Transfer of lymphoid cells from strain-2 guinea pigs immunized to bovine gamma globulin into syngeneic recipients immunized with dinitrophenyl ovalbumin markedly enhances the secondary antidinitrophenyl response of the recipient to challenge with dinitrophenyl-bovine gamma globulin. This function of the carrier bovine gamma globulin-specific cells is resistant to irradiation with up to 5000 rads, although the capacity of the irradiated cell population to transfer immunologic memory for bovine gamma globulins or to be stimulated by antigen to synthesize DNA in vitro is abolished by this treatment.

On a model for ontogenic development.

A theory to explain both the endogenous control of differentiation and programmed organismal aging as the result of one fundamental regulatory mechanism is advanced. It is postulated that these phenomena are linked to cell division, which is presumed to be the primary unit of measurement for the organism's maturation and aging. The hypothesis developed here holds that a genetic locus (DSI), modulating both cell division and enzyme induction, is first activated and then inactivated with each cycle. The number of DSIs in the genome of each cell is finite, cellular sensescence occurring when the genome is depleted of functional DSIs. Protein inducers are linked to specific DSIs, which are only transcribed at appropriate times during ontogeny, this in turn being a function of the number of DSIs previously inactivated during earlier mitoses. Experimental approaches which could test this model are discussed.

Determination of antibody avidity at the cellular level by the plaque inhibition technique: effect of valence of the inhibitor.

Inhibition of plaque formation by multivalent and univalent ligands was compared as an assay of avidity of antibody produced by PFC. Multivalent ligands are much more effective as inhibitors and their use tends to impart an appearance of lack of heterogeneity and high avidity to the PFC populations being studied. It is thus probably generally advisable to employ univalent ligands in such studies.

Production of auto-anti-idiotypic antibody during the normal immune response. XII. An enzyme-linked immunosorbent assay for auto-anti-idiotype antibody.

An enzyme-linked immunosorbent assay (ELISA) to detect anti-idiotype (Id) antibody is described. Using this assay auto-anti-Id was detected in the serum of aged mice immunized with 2,4,6-trinitrophenylated-Ficoll (TNP-F). Hapten eluates from anti-TNP-F immune spleen cells also contained readily detectable auto-anti-Id.

Production of auto-anti-idiotypic antibody during the normal immune response. VI. Hapten augmentation of plaque formation and hapten-reversible inhibition of plaque formation as assays for anti-idiotype antibody.

(1) Evidence has been presented that the detection of hapten-augmentable plaques indicates cells whose secretion of antibody had been blocked by the binding of auto-anti-id to cell surface idiotypes. Because of the dependence of the assay on the affinities of the various species for one another, the number of hapten-augmentable plaques detected should be regarded as a minimal estimate of the number of cells whose secretion of antibody is inhibited by auto-anti-id. For confirmation that hapten-augmentable PFC are due to auto-anti-id 2 principal controls are important: (a) incubation of the spleen cell population with hapten prior to plaquing should remove the hapten-augmentable PFC; (b) the dialyzed supernate from hapten incubated cells should inhibit plaque formation in a hapten-reversible manner. (2) Evidence has been presented that hapten-reversible inhibition of plaque formation can serve as an assay for anti-id. Apparent false positive assays can result from the presence of anti-hapten antibody or antigen-antibody complexes; however, these apparent false positives are rarely reversed by hapten. Removal of anti-hapten antibody, by passage over an antigen immunoadsorbent, will eliminate this source of false positives and the procedure is recommended. False negative results can arise from mismatching of the anti-ids in the sample to be assayed and the idiotypes of the target cells used in the assay. This can result from shifts in idiotype expression related to age and time after antigen injection. False negatives can also result from the presence of idiotype-anti-id complexes in the sample to be assayed. This source of false negatives can sometimes be eliminated by passage of the sample through an antigen immunoadsorbent.

Delayed maturation of the antibody response to type 2 thymus-independent antigens in a partially inbred strain of chicken.

The ontogeny of antibody responses to trinitrophenylated (TNP) thymus-independent (TI) antigens was compared in two partially inbred strains of chicken: the SC strain (B2/B2 genotype) and the FP strain (B15/B22 genotype). In the SC chicken, maturation of both the splenic anti-TNP plaque-forming cell (PFC) response and the 19S hemagglutinating antibody response to TI type 2 (TI-2) antigens, TNP-Ficoll and TNP-dextran, were delayed to a significantly later time in ontogeny (20 wk of age) than in the FP chickens (9 wk of age). Four- to 6-wk-old SC chickens were virtually immunologically unresponsive to stimulation with TI-2 antigens. The TI-1 antigen TNP-Brucella abortus was equally immunogenic in both FP and SC chickens of different age groups tested. Kinetic studies of the primary PFC response to TNP-Ficoll in immunologically mature chickens of the SC and FP strains demonstrated a peak PFC response 4 days after antigen injection, followed by a rapid decline in numbers of splenic PFC/spleen on day 6. The results of these studies are discussed in relation to earlier observations that suggested there may be a delay or a defect in the ontogeny of the thymus in the SC chicken.