Idiotypic analysis of hybridoma antibodies to branched synthetic polymer (Tyr, Glu)-Ala-Lys: idiotypic relationship with antibodies to linear random polymer (Glu60, Ala30, Tyr10)

The expression of three anti-GAT idiotypes, CGAT, Gte, and GA-1, on 17 C57BL/10 and four C3H.SW hybridoma anti-(T,G)-A--L antibodies was analyzed. These hybridoma anti-(T,G)-A--L antibodies exhibited two patterns of fine antigen binding specificity. The majority of the hybridoma antibodies bound the (T,G)-A--L, GT, and GAT polymers but not the GA polymer, and were designated as GT-reactive hybridoma antibodies. A minor population of hybridoma anti(T,G)-A--L antibodies bound to (T,G)-A--L but not to GT, GAT, or GA, i.e., (T,G)-A--L-specific. A complete correlation between fine antigen binding pattern and the expression of CGAT idiotype was demonstrated. None of the 21 hybridoma anti-(T,G)-A--L antibodies expressed the GA-1 idiotype. All of the GT-reactive and none of the GT-nonreactive hybridoma anti-(%,G)-A--L antibodies expressed the CGAT idiotype. Furthermore, the Gte idiotype was found on the majority of CGAT+-bearing C57BL/10 hybridoma anti-(T,G)-A--L antibodies. These results indicate that C57BL/10 anti-(T,G)-A--L antibody repertoire can be grouped into a minimum of three families; i.e., CGAT+ Gte+, CGAT+ Gte-, and CGAT- Gte- families, with the CGAT+ Gte+ family as the major compartment. This is confirmed by the high percentage idiotype binding of serum anti-(T,G)-A--L antibodies with anti-CGAT idiotypic antisera. Finally, anti-idiotypic antisera made against CGAT+ hybridoma anti-GAT or anti-(T,G)-A--L antibodies crossreact extensively with other CGAT+ hybridoma anti-GAT and anti-(T,G)-A--L antibodies. However, additional experiments demonstrated that CGAT+ hybridoma anti-(T,G)-A--L antibodies also possess private idiotypes.     

Cross-reactive idiotypic determinants on antibodies and antigen-specific helper T cell continuous lines

Anti-idiotypic antibodies produced in C57BL/6 mice (H-2b, Igh-1b) against (T,G)-A--L-specific antibodies of C3H.SW mice (H-2b, Igh-1j) were used to probe (T,G)-A--L-specific helper T cell lines and clones for the expression of idiotypic determinants on the cell surface of the monoclonal functional T cells. By using the fluorescence-activated cell sorter (FACS II), anti-idiotypic sera of individual mice that specifically bind C3H.SW anti-(T,G)-A--L antibodies were shown to stain significantly cells of the E-9M(+) continuous T helper line originated from C3H.SW (T,G)-A--L "educated" T cells. The same antisera did not react with a helper T cell line of C3H.SW origin specific to human gamma-globulin. They also did not stain a (T,G)-A--L-specific helper T cell line derived from CWB (H-2b, Igh-1b) mice, which differ from C3H.SW mice only in their heavy chain allotypes. Thus, the expression of the idiotypic determinants on the T cell lines appears to be antigen-specific and linked to the heavy chain allotypic marker as shown for the specific antibodies. Different clones derived from the E-9 M(+) line were tested their reactivity with the individual anti-idiotypic sera. All clones but one (1.11) were stained significantly. The clones were tested for their biologic activity and all of them except clone 1.11 were found to exert helper activity specific to (T,G)-A--L. Thus, individual anti-idiotypic sera against C3H.SW anti-(T,G)-A--L antibodies recognize cross-reactive idiotypic structures on the surface of antigen-specific monoclonal helper T cells.     

Variable regions of antibodies to synthetic polypeptides. II. Analysis of variable region genes encoding antibodies specific for (T,G)-A--L

Monoclonal antibodies specific for the synthetic polypeptide antigen (T,G)-A--L have been produced in two strains of mice, C57BL/10 and C3H.SW. The genes encoding the variable (V) regions of these antibodies have been studied by using the DNA hybridization technique of Southern, as well as by gene cloning and sequencing. Hybridization of DNA from 14 different cell lines with a kappa-chain probe revealed that the different cell lines used one of two different gene rearrangements to encode the recombined V region gene. There was a perfect correlation between light chain rearrangement, idiotype expression, and fine specificity. Hybridization analyses of the heavy chain revealed a more complex pattern. Seven hybridomas had the rearranged heavy chain V region genes on a 4.4 kb EcoRI restriction fragment. Others were found on restriction fragments that differed in length by several hundred base pairs. The recombined heavy chain V region genes were cloned from three different hybridoma cell lines secreting anti-(T,G)-A--L antibodies, all of which express the same idiotype and fine specificity pattern. Restriction mapping and sequencing indicate that all three utilize the same V gene, identified as the 186-2 germline gene. However, different D and J genes are used to encode each of the antibodies. In contrast to the results seen in other antigen systems, heavy chain D and J genes do not have a major influence on idiotype expression and fine specificity of antibodies to the synthetic polypeptide (T,G)-A--L.     

Anti-idiotype stimulation of antigen-specific antigen-independent antibody responses in vitro. II. Triggering of B lymphocytes by idiotype plus anti-idiotype in the absence of T lymphocytes

Antibodies specific for the idiotypes of B10 anti-(T,G)-A--L antibodies (anti-id) induced B lymphocytes to secrete anti-(T,G)-A--L antibodies in vitro in the absence of both antigen and T lymphocytes, provided either that the B lymphocytes were previously primed in vivo with (T,G)-A--L or that id specific for (T,G)-A--L was added to the cultures. These antigen- and T lymphocyte-independent responses were antigen specific and appeared not to require accessory cells. The results suggested that B lymphocyte activation occurred via the formation of id-anti-id complexes, and evidence was obtained that this activation involved two separate interactions between the B lymphocytes and the id-anti-id complexes. These studies document a previously undescribed regulatory function of anti-idiotype antibodies.     

Xid and normal mice express a light chain-associated cross-reactive idiotype in response to (T,G)-A--L and (T,G)-A--L-mBSA

Rabbit anti-idiotypic (Id) antibodies were prepared against purified ascites anti-(T,G)-A--L antibodies (TGB5) that had been absorbed to remove A--L-specific antibodies and were specific for (T,G)-side chain determinants. Purified rabbit anti-TGB5 Id antibodies detected an allotype-independent, light chain-associated cross-reactive Id expressed by the majority of individual mice immunized with (T,G)-A--L, (T,G)-A--L coupled to methylated bovine serum albumin (mBSA), or the linear terpolymer GAT. Primary and secondary monoclonal hybridoma protein (HP) antibodies from X/Xxid heterozygous (wild-type) mice immunized with (T,G)-A--L and/or (T,G)-A--L-mBSA were analyzed for isotypy and were grouped into eight antibody fine specificity sets defined by the patterns of direct binding to the antigens (T,G)-A--L, (Phe,G)-A--L, (T,G)-Pro--L, GT, and A--L. Analysis of these primary and secondary HP for TGB5 idiotypy showed a preferential expression of the TGB5 Id among GT+-binding HP (antibody fine specificity sets 1 through 3). All of the primary GT+-binding HP and the majority of secondary GT+-binding HP (sets 1 through 3) were TGB5 Id+. Most but not all of the TGB5 Id+ HP bound GAT. Of the side-chain-specific HP (sets 1 through 7), 78% of primary HP vs 49% of secondary HP bound GT. By these criteria, the primary HP response appears more restricted than the secondary HP response, consistent with the idea that Id diversification and antibody heterogeneity are regulated and selected events occurring during memory B cell generation. Although xid mice produce less antibody than wild-type mice to (T,G)-A--L, the TGB5 Id was produced early in the primary response by both xid and wild-type mice immunized with (T,G)-A--L or (T,G)-A--L-mBSA, and was maintained as a detectable Id in equivalent amounts in their secondary serum antibody responses. These results support the idea that distinct B cell subsets, including the xid B cell subset, share the same immunoglobulin gene repertoire.     

Genetic control of the immune response to (T,G)-A--L in C3H in equilibrium C57 tetraparental mice

When 15 C3H ? C57 tetraparental (allophenic) mice were analyzed for coat color, hemoglobin, and immunoglobulin allotype, all but two were shown to be chimeric. These 15 tetraparental mice were immunized with the synthetic polypeptide (T,G)-A--L, and the origin of the (T,G)-A--L-specific antibody produced was determined by using genetic markers (allotypes) on the immunoglobulin heavy chain constant region. Five tetraparental mice were high responders to (T,G)-A--L and had significant amounts of a (low responder) allotype antibody in their total serum. Three of these mice had significant amounts of anti-(T,G)-A--L antibody of the a (low responder) allotype. The antigen binding capacities of the a allotype fractions of these three were 4–5 times higher than the antigen binding capacities of immunized C3H (low responder) control mice. These results are compatible with the hypothesis that the inability of low-responder mice to produce significant amounts of anti-(T,G)-A--L antibody is a function of Ir-1A gene expression at the level of T cells.     

Clonal analysis of the primary and secondary B cell responses of neonatal, adult, and xid mice to (T,G)-A--L

The splenic focus assay was used to clone B cells from neonatal, adult and xid mice in order to examine their primary and secondary responses to (T,G)-A--L. Adult precursor cell frequencies to (T,G)-A--L were achieved late in neonatal ontogeny. Primary xid B cells responded to DNP-HY but not to (T,G)-A--L in the splenic focus assay. The frequency of secondary B cells from (T,G)-A--L-primed xid mice was less than or equal to 10% that of secondary B cells from wild-type (non-xid or X/Xxid heterozygous) mice. Although xid B cells were poorly responsive to (T,G)-A--L in the splenic focus assay, (T,G)-A--L-primed xid mice could provide help as recipients for stimulation of wild-type primary and secondary B cells. It seems likely that the B2 subset contributes most of the splenic focus response to (T,G)-A--L. The fine specificities of antibodies produced by neonatal, xid, and adult (wild-type) B cell clones were analyzed using analogues of (T,G)-A--L. A specificity shift was observed between the adult primary and secondary antibody responses to (T,G)-A--L. Less than 10% of adult primary clones produced antibodies cross-reactive on (Phe,G)-A--L (recognizing A--L determinants or Phe,Glu determinants), whereas more than 70% of primary clones produced Tyr,Glu side-chain specific antibodies cross-reactive on GT. The percentage of clones producing GT-binding antibodies diminished in the secondary response, while the percentage of clones producing antibodies cross-reacting on (Phe,G)-A--L increased. Neonatal clones also produced mostly GT-binding antibodies but gave a higher percentage of (Phe,G)-A--L-cross-reacting antibodies than adult primary clones. The specificities of secondary antibodies produced by xid and wild-type B cell clones were dissimilar. First, xid secondary clones were "primary-like" in that no anti-A--L antibodies were detected. Second, clones whose antibodies bound side-chain determinants but not GT were produced in higher frequency by xid than by wild-type secondary B cells. The differential responsiveness of B cell subsets to antigen and regulatory signals may influence memory B cell generation and the specificity of antibodies produced in the primary vs secondary response.     

Fine specificity of antibodies to the synthetic polypeptide poly(L-tyrosine, L-glutamic acid)-poly(DL-alanine)--poly(L-lysine) and its ordered analogs as followed by solid-phase radioimmunoassay

The fine specificity of antibodies against (T,G)-A--L and its ordered analogs (T-T-G-G)-A--L and (T-G-T-G)-A--L was studied. Fifty percent of the antibodies against (T,G)-A--L are directed toward the T-T-G-G determinants and 19% against T-G-T-G-like determinants. The rest of the antibody response to (T,G)-A--L is directed against determinants which exist in (T,G)-A--L but are not cross-reactive with either T-T-G-G- or T-G-T-G-like determinants. Although (T-T-G-G)-A--L and (T-G-T-G)-A--L differ only in the sequence of tyrosine and glutamic acid in their side chains, no crossreactivity was observed between antibodies toward the two ordered polypeptide antigens.     

Antigen-specific T cell factors: a fine analysis of specificity.

The specificity of T cell factors produced in presence of synthetic polypeptide antigens was studied. Factors prepared with either one of the three antigens: poly(Tyr,Glu)-poly(DLALa)--poly(Lys), (T,G)-A--L, poly(Phe,Glu)-poly(DLALa)--poly(Lys), (Phe,G)-A--L, and poly(His,Glu)-poly(DLALa)--poly(Lys), (H,G)-A--L, successfully cooperated with B cells for antibody production to the homologous as well as to the other two immunogens. Furthermore, the activity of a (T,G)-A--L-specific factor was removed after passage through immunoadsorbents built of Sepharose coupled to: (T,G)A--L, (Phe-G)-A--L and poly(Glu)-poly(DLAa)--poly(Lys), (G)-A--L, but not to poly (DLALa)--poly(LLys),A--L. No cross-reactivity was observed between (T,G)-A--L and poly(Tyr,Glu)-poly(Pro)--poly(Lys), (T,G)-Pro--L, at the level of T cell factors, as shown using the above approaches. These results lead to the conclusion that specificity of T cell factors, although not identical, is similar to that of antibodies.     

Genetic control of immune responsiveness to poly (LPro)--poly (LLys)-derived polypeptides by histocompatibility-linked immune response genes in the rat.

In rats responsiveness to branched synthetic polypeptides carrying a Pro--L backbone, such as (T,G)-Pro--L or (Phe,G)-Pro-L and to Pro--L itself is controlled by Ir genes which are linked to the major histocompatibility genes. The level of antibody production to these polypeptides does not fall into strict high or low responder categories but covers the range in between. (T,G)-pro--L and Pro--L elicit a very similar response pattern which, however, differs from that obtained with (Phe,G)-Pro--L. Anti-(T,G),Pro--L antibodies do not cross-react with (T,G)-A--L, but do so extensively with Pro--L. Anti-(Phe,G)-Pro--L antibodies show cross-reactivity to (Phe,G)-A--L only when the antibody-producing strain is a high responder to (Phe,G)-A--L. These results when considered in view of data obtained in mice on genetic control of the immune response to (T,G)-Pro--L suggest that at least two unlinked Ir genes are involved in controlling anti-Pro--L responsiveness.     

Specificity of H-2-linked Ir gene control in mice: demonstration of T helper cells recognizing branched synthetic polypeptides in low responder mice

This report provides evidence for the presence of T helper cells capable of recognizing the polypeptide antigens T6-A--L and (H,G)-A--L in low responder mice of H-2k and H-2b haplotypes, respectively. Mice were primed in vivo with the T6-A--L-avidin-(H,G)-A--L complex or, in the case of T6-A--L in H-2k mice, with the cross-reactive and permissive antigen T6-S--L. T helper cells cooperating with DNP-primed B cells could be rechallenged in vitro with the DNP-conjugates of T6--A--L or (H,G)-A--L, although the cells were of low responder type with respect to these antigens. This implies that T cell-macrophage interaction required for restimulation is apparently not defective in these low responders. The implications of these results for the concept of Ir gene control are discussed.     

Characterization and biologic activities of an anti-idiotype-specific T cell line and its derived clones

Monoclonal anti-idiotypic antibodies were prepared against monoclonal antibodies (mAb103) specific to the synthetic polypeptide antigen (T,G)-A-L. A cell line was established by the stimulation of C3H.SW mouse T cells with one of the monoclonal anti-idiotypes (mAbA-6) that reacted with both mAb103 and conventional (T,G)-A-L-specific antibodies. The T cell line proliferated specifically in the presence of the homologous mAbA-6 and to a lesser degree when triggered with (T,G)-A-L. The line could help (T,G)-A-L primed B cells in the production of (T,G)-A-L-specific antibodies when stimulated in vitro with either (T,G)-A-L or mAbA-6. Clones obtained from the line were stimulated and maintained in culture in presence of mAbA-6 whereas others were stimulated and grown in the presence of (T,G)-A-L. Both types of clones proliferated only in the presence of mAbA-6 although (T,G)-A-L could inhibit efficiently and specifically the latter proliferation. A significant number of the (T,G)-A-L-stimulated clones could collaborate with (T,G)-A-L primed B cells in the presence of either (T,G)-A-L or mAbA-6 for the production of specific antibodies. Immunoblotting experiments indicated that mAbA-6 reacted with both the T cell receptor of the mAbA-6-specific T cell line and of a (T,G)-A-L-specific T cell line but not with that of a line specific to a nonrelated antigen.     

Alteration in H chain V region affects complement activation by chimeric antibodies

Chimeric antibodies to the synthetic polypeptide (Tyr, Glu)-Ala-Lys ((T,G)-A-L) were used to examine C activation by human IgG1. Two IgG1 antibodies, which contained mouse L chains and H chains with mouse V domains and human C domains, differed only in their VH domain. Ag binding and C activation by these antibodies were analyzed by ELISA. When limiting amounts of Ag were used in the assays, the antibodies required different quantities of Ag for optimal binding, suggesting that the antibodies bind to different epitopes on the (T,G)-A-L molecule. However, when competitive inhibition assays were performed with an optimal concentration of Ag, there were no differences in relative binding affinities for (T,G)-A-L or dissociation characteristics of the antibodies. C activation was examined at optimal Ag concentration to ensure equivalent binding of two IgG1 antibodies to Ag. After combination with immobilized Ag, these two antibodies bearing different V regions exhibited marked differences in the binding of C components C1q and C3d. When present in equal amounts in the assay, antibody 10B activated C and bound more C1q and C3d than antibody B11. These results indicate that V region differences can affect C activation by IgG.     

The role of the idiotypic network in the induction of experimental systemic lupus erythematosus

Systemic lupus erythematosus (SLE) has been induced in C3H.SW mice by their immunization with a human monoclonal anti-DNA antibody that bears a common idiotype-16/6 Id. Following immunization, high levels of murine anti-16/6 and anti-anti-16/6 antibodies were detected in the sera of the immunized mice. Elevated titers of autoantibodies reacting with ssDNA, dsDNA, poly(I), poly(G), RNP, Ro, and La were also observed. The serological findings were associated with significant proteinuria, leukopenia, and elevated erythrocyte sedimentation rate. Immune complex deposition in the glomerular mesangium and sclerosis of the glomeruli were demonstrated. To study whether or not anti-idiotype antibodies are involved in the induction of the disease, a murine monoclonal antibody against the 16/6 Id was prepared and injected into C3H.SW mice. The anti-16/6 Id antibody induced experimental SLE similarly to the 16/6 Id with an accelerated kidney pathology. A study performed on different mouse strains indicated that the susceptibility to the induction of SLE by the 16/6 Id is strain dependent and directly correlates to their ability to produce anti-16/6 Id specific antibodies.     

Human prorenin has "gate and handle" regions for its non-proteolytic activation

We investigated the mechanism for non-proteolytic activation of human prorenin using five kinds of antibodies. Each of the antigens, L1PPTDTTTFKRI11P, T7PFKRIFLKRMP17P, I11PFLKRMPSIRESLKER26P, M16PPSIRESLKER26P, and G27PVDMARLGPEWSQPM41P, was designed from the tertiary structure of predicted prorenin. These antibodies were labeled anti-01/06, anti-07/10, anti-11/26, anti-16/26, and anti-27/41, respectively, for their binding specificities. Inactive recombinant human prorenin (0.1 nM) bound to various concentrations of anti-01/06, anti-11/26, and anti-27/41 antibodies at 4 degrees C with equilibrium dissociation constants of 138, 41, and 22 nM, respectively. However, intact prorenin (0.1 nM) did not show significant binding to 200 nM anti-07/10 and anti-16/26 antibodies for 20 h. Ninety percent of prorenin (0.1 nM) was found to be non-proteolytically activated by incubation with anti-11/26 antibodies (200 nM) at 4 degrees C for 20 h. Prorenin was not active even under complex with either anti-01/06 or anti-27/41 antibodies. Prorenin was also reversibly activated at pH 3.3 and 4 degrees C for 25 h. The acid-activated prorenin bound to anti-07/10 and anti-16/26 antibodies as well as to anti-01/06, anti-11/15, and anti-27/41 antibodies at neutral pH and 4 degrees C in 2 h. Their dissociation constants were 13, 40, 8.6, 3.6, and 14 nM, respectively. The acid-activated prorenin was re-inactivated by incubation at pH 7.4 and 4 degrees C in 50 h. Anti-07/10 and anti-11/26 antibodies inhibited such re-inactivation at 25 degrees C by more than 90% and 50%, respectively, whereas other kinds of antibodies did not prevent the re-inactivation at 25 degrees C. These results indicate that prorenin has "gate" (T7PFKR10P) and "handle" (I11PFLKR15P) regions critical for its non-proteolytic activation.     

Identification of Serotonin Receptors Recognized by Anti-Idiotypic Antibodies

Anti-idiotypic antibodies were generated by immunizing rabbits with affinity-purified antibodies to serotonin (5-hydroxytryptamine; 5-HT). Anti-5-HT activity was removed from the resulting antisera by chromatography through a 5-HT affinity column. The anti-idiotypic antibodies were demonstrated by enzyme-linked immunosorbent assay to bind to affinity-purified whole anti-5-HT antibodies and their Fab fragments. Anti-idiotypic antibodies, purified by affinity chromatography on columns to which antibodies to 5-HT were coupled, competed with 5-HT (covalently bound to protein) for the binding sites on anti-5-HT antibodies and serotonin binding protein. The anti-idiotypic antibodies antagonized the binding of [3H]5-HT to membranes isolated from the cerebral cortex, striatum, and raphe area more than to membranes from hippocampus or cerebellum. The anti-idiotypic antibodies also blocked the binding of the 5-HT1B-selective ligand (-)-[125I]iodocyanopindolol (in the presence of 30 microM isoproterenol) to cortical membranes. In contrast, anti-idiotypic antibodies failed to inhibit binding of the 5-HT1A-selective ligand 8-hydroxy-2-(di-n-[3H]propylamino)-tetralin [( 3H]8-OH-DPAT) to raphe area membranes or hippocampal membranes. These observations suggested that the anti-idiotypic antibodies may recognize some 5-HT receptor subtypes but not others. This hypothesis was tested by ascertaining the ability of anti-idiotypic antibodies to immunostain cells transfected in vitro with cDNA encoding the 5-HT1C or 5-HT2 receptor or with a genomic clone encoding the 5-HT1A receptor. Punctate sites of immunofluorescence were found on the surfaces of fibroblasts that expressed 5-HT1C and 5-HT2 receptors, but not on the surfaces of HeLa cells that expressed 5-HT1A receptors. Immunostaining of cells by the anti-idiotypic antibodies was inhibited by appropriate pharmacological agents: immunostaining of cells expressing 5-HT1C receptors was blocked by mesulergine (but not ketanserin, 8-OH-DPAT, or spiperone), whereas that of cells expressing 5-HT2 receptors was blocked by ketanserin or spiperone (but not mesulergine or 8-OH-DPAT). The anti-idiotypic antibodies failed to inhibit the uptake of [3H]5-HT by serotonergic neurons. It is concluded that the anti-idiotypic antibodies generated with anti-5-HT serum recognize the 5-HT1B, 5-HT1C, and 5-HT2 receptor subtypes; however, neither 5-HT1A receptors nor 5-HT uptake sites appear to react with these antibodies.     

Functional requirements of (Phe,G)-A--L-specific T-cell clones of (H-2 b x H-2 kF1 origin

T-cell clones specific for the synthetic polypeptide antigen poly(LPhe, LGlu)-poly(DLAla)--poly(LLys) of (C57BL/6 x C3H/HeJ)F₁ origin were tested for their biological activities. One group of clones was restricted in its proliferative response to the H-2 ^b haplotype, the second to the H-2 ^k haplotype, and the third to the F₁ unique Ia determinants. All the clones which proliferated in response to antigen secreted interleukin-2 (IL-2) following stimulation. The H-2 restriction of the IL-2 secretion was the same as that of the proliferation. Two of the clones tested, C.6 and C.10, could provide help to B cells in antibody production. However, the genetic restriction profile of the helper activity was less stringent than that for the proliferative response. Thus, C.6, which proliferated in the presence of F₁ antigen-presenting cells only, could help B cells and accessory cells of C3H/HeJ. C.10, which was restricted in its proliferative response to the H-2 ^b haplotype, could collaborate with B cells and accessory cells of the H-2 ^k haplotype as well. The antibody response of both clones was restricted to the parental or F₁ strains.Abbreviations used in this paper (T, G)-A-L poly-(LTyr, LGlu)poly(DLAla)--poly(LLys) - (Phe, G)-A--L poly(LPhe, LGlu)-poly(DLAla)--poly(LLys) - APC antigen-presenting cells - Con A concanavalin A - FCS fetal calf serum - IL-2 interleukin-2     

Quantitative differences in the expression of a 72,000 molecular weight cell surface glycoprotein (GP72) in Trypanosoma cruzi zymodemes

A high affinity monoclonal antibody, 8G2 B9, was used to assess the expression of a 72,000 m.w. glycoprotein ( GP72 ) in isoenzyme-typed T. cruzi strains ( zymodemes ). Western blotting analysis of T. cruzi clones showed that 8G2 B9 bound strongly to GP72 and also suggested that this antigen was absent or weakly detectable in T. cruzi zymodeme 1 (Z1) strains. Purified 8G2 B9 was radiolabeled with 125I and used in an inhibition radioimmune binding assay to compare the quantities of GP72 in different zymodemes . Ninety-six T. cruzi strains were assayed, of which 36 were Z1, 36 were Z2, five were Z3 , and 19 were Z2 (heterozygous). Most (64%) Z1 strains lacked detectable GP72 , whereas this antigen was always detected Z2 and Z2 (heterozygous) strains. There was an 18-fold difference between geometric mean values for the quantities of GP72 (expressed as nanograms per milligram total cell protein) in Z1 and Z2 strains (Z1, 36 ng/mg; Z2, 639 ng/mg; p less than 0.001). There were also significant differences between the geometric mean values for Z2 and Z2 (heterozygous) strains, i.e., 639 ng/mg and 1648 ng/mg, respectively (p less than 0.001). GP72 was detected in four of the Z3 strains in quantities ranging from 740 to 3640 ng/mg. The absolute amounts of antigen in GP72 -positive strains were low, comprising less than 1% of the total cell protein. The specificities of two other anti- GP72 monoclonal antibodies, 7C6 D7 and WIC 29.26, were compared with 8G2 B9. Both antibodies completely inhibited the binding of 8G2 B9 to GP72 in solid phase immunoassays, suggesting that they reacted with the same antigenic determinants. The results show that monoclonal antibody-based assessments of the expression of GP72 correlate with zymodeme classification, and they also suggest that the monoclonal antibodies recognize major antigenic determinants on GP72 . It should be possible to use 8G2 B9 as an immunologic marker to additionally investigate the clinical significance of T. cruzi zymodemes and the biologic significance of GP72 .     

Establishment of internal-image anti-idiotype monoclonal antibodies to a human antibody to lung cancer

 Internal-image anti-idiotype antibodies are expected to enhance anticancer effector mechanisms in vivo. The objective of this study was to establish hybridomas producing anti-idiotype monoclonal antibodies against a human monoclonal antibody (hmAb) 4G12 that reacts strongly with lung squamous cell carcinomas. BALB/c female mice 6 weeks old were immunized with 4G12. Splenocytes were hybridized with P3U1 cells and hybrid cells secreting anti-4G12 hmAb were cloned. Two clones reacted with 4G12 hmAb but not with 3H12 IgM hmAb, human IgM, human serum or fetal calf serum. These two Ab2 antibodies (IgG1κ) 2B12 and 2H1 demonstrated 91.5% and 90.3% inhibition in their reactivity with radiolabelled 4G12 on PC10 cells, indicating that 2B12 and 2H1 antibodies were of the Ab2β type. In criss-cross inhibition assays, the binding of 2B12 or 2H1 to 4G12 was not inhibited by 2H1 or 2B12. Thus 2B12 and 2H1 were thought to recognize the different epitopes on the antigen-binding sites. Antisera against 2B12 and 2H1 demonstrated specific reactivity to PC10 cells. The two Ab2β antibodies, 2B12 and 2H1, express internal images of lung squamous cell carcinoma recognized by the 4G12 antibody and may be useful for cancer immunotherapy. Received: 20 September 1996 / Accepted: 2 January 1997     

Molecular analysis of heavy and light chains used by primary and secondary anti-(T,G)-A--L antibodies produced by normal and xid mice

The primary (1 degree) antibody response to (T,G)-A--L shows limited heterogeneity, consisting mostly of side chain-specific antibodies that bind GT and that express the TGB5 idiotype (Id). The secondary (2 degrees) response is very diverse: antibodies that bind the backbone A--L constitute a third of the response, and a high proportion of the side chain-specific antibodies do not bind GT and are TGB5 Id-. To provide a molecular basis for understanding this difference in repertoire expression, we analyzed the Ig genes used by heavy and light chains of 1 degree and 2 degrees side chain-specific anti-(T,G)-A--L hybridoma antibodies (HP). Southern blot restriction analysis and nucleotide sequence analysis of the expressed genes used by three TGB5 Id+ 2 degrees HP showed usage of three different VH genes in two VH gene families (36-60 and J558), different D segments, and two different Vk1 genes (the Vk1A and Vk1C subgroups). Thus, antibody heterogeneity in the 2 degrees response is contributed by combinatorial diversity of distinct germ-line genes. Nucleotide sequence analysis of the expressed genes used by TGB5 Id+ 1 degree HP showed use of highly homologous VH genes in the J558 VH gene family and highly homologous Vk1A genes. The majority of TGB5 Id+ 1 degree HP from different donors gave similar heavy and similar light chain gene rearrangements by Southern blot restriction analysis, after correction for known or potential J region differences. The combined nucleotide sequence and Southern blot restriction analysis data suggest that most 1 degree B cells use the same or very similar VH and Vk genes, i.e., the 1 degree response is paucigenic. Different D segments were used by the TGB5 Id+ 1 degree and 2 degrees HP that were sequenced, and there was no apparent correlation between TGB5 idiotypy and VH, D gene, or JH gene usage. However, all TGB5 Id+ HP sequenced used highly homologous genes from the Vk1 group. Expression of a Vk1 light chain correlates with, but is not sufficient for, TGB5 idiotypy, because one GT-binding, TGB5 Id- HP was found to use a Vk1C subgroup light chain. By Southern blot and nucleotide sequence analysis, the Vk genes used by two TGB5 Id+ 2 degrees HP from xid mice are highly homologous, if not identical to the Vk1A gene(s) used by 1 degree and 2 degrees Id+ HP from wild-type mice.