Lentiviral-mediated gene therapy leads to improvement of B-cell functionality in a murine model of Wiskott-Aldrich syndrome

BACKGROUND

Wiskott-Aldrich syndrome (WAS) is an X-linked primary immunodeficiency characterized by thrombocytopenia, eczema, infections, autoimmunity, and lymphomas. Transplantation of hematopoietic stem cells from HLA-identical donors is curative, but it is not available to all patients. We have developed a gene therapy (GT) approach for WAS by using a lentiviral vector encoding for human WAS promoter/cDNA (w1.6W) and demonstrated its preclinical efficacy and safety.

OBJECTIVE

To evaluate B-cell reconstitution and correction of B-cell phenotype in GT-treated mice.

METHODS

We transplanted Was(-/-) mice sublethally irradiated (700 rads) with lineage marker-depleted bone marrow wild-type cells, Was(-/-) cells untransduced or transduced with the w1.6W lentiviral vector and analyzed B-cell reconstitution in bone marrow, spleen, and peritoneum.

RESULTS

Here we show that WAS protein(+) B cells were present in central and peripheral B-cell compartments from GT-treated mice and displayed the strongest selective advantage in the splenic marginal zone and peritoneal B1 cell subsets. After GT, splenic architecture was improved and B-cell functions were restored, as demonstrated by the improved antibody response to pneumococcal antigens and the reduction of serum IgG autoantibodies.

CONCLUSION

WAS GT leads to improvement of B-cell functions, even in the presence of a mixed chimerism, further validating the clinical application of the w1.6W lentiviral vector.

Nasal cholera toxin elicits IL-5 and IL-5 receptor alpha-chain expressing B-1a B cells for innate mucosal IgA antibody responses

In this study, we examine whether native cholera toxin (nCT) as a mucosal adjuvant can support trinitrophenyl (TNP)-LPS-specific mucosal immune responses. C57BL/6 mice were given nasal TNP-LPS in the presence or absence of nCT. Five days later, significantly higher levels of TNP-specific mucosal IgA Ab responses were induced in the nasal washes, saliva, and plasma of mice given nCT plus TNP-LPS than in those given TNP-LPS alone. High numbers of TNP-specific IgA Ab-forming cells were also detected in mucosal tissues such as the nasal passages (NPs), the submandibular glands (SMGs), and nasopharyngeal-associated lymphoreticular tissue of mice given nCT. Flow cytometric analysis showed that higher numbers of surface IgA+, CD5+ B cells (B-1a B cells) in SMGs and NPs of mice given nasal TNP-LPS plus nCT than in those given TNP-LPS alone. Furthermore, increased levels of IL-5R alpha-chain were expressed by B-1a B cells in SMGs and NPs of mice given nasal TNP-LPS plus nCT. Thus, CD4+ T cells from these mucosal effector lymphoid tissues produce high levels of IL-5 at both protein and mRNA levels. When mice were treated with anti-IL-5 mAb, significant reductions in TNP-specific mucosal IgA Ab responses were noted in external secretions. These findings show that nasal nCT as an adjuvant enhances mucosal immune responses to a T cell-independent Ag due to the cross-talk between IL-5Ralpha+ B-1a B cells and IL-5-producing CD4+ T cells in the mucosal effector lymphoid tissues.

Antibody repertoire development in fetal and neonatal piglets. IX. Three pathogen-associated molecular patterns act synergistically to allow germfree piglets to respond to type 2 thymus-independent and thymus-dependent antigens

Newborn piglets maintained germfree (GF) cannot respond to either thymus-dependent (TD) or type 2 thymus-independent Ags (TI-2) unless colonized with bacteria. We show here that pathogen-associated molecular patterns (PAMPs), including muramyl dipeptide (MDP), LPS, and a B-class CpG oligonucleotide (CpG-B), can substitute for gut flora in the induction of neonatal immunoresponsiveness. These PAMPs alone or in combination had little effect on serum IgG and IgA levels, but CpG-B and CpG-B + MDP elevated total IgM levels 3- to 7-fold above that seen in colonized controls after booster immunization. Although only CpG-B could alone stimulate immunoresponsiveness, co-administration of LPS or MDP resulted in a 5-fold increase in the IgG response to both immunogens. Co-administered MDP did not promote secondary IgG responses to either Ag but instead pronounced secondary IgM responses to the epitopes of both immunogens. LPS co-administered with CpG-B may promote class switch recombination or cause differentiation of previously switched cells that become responsive after exposure to CpG-B. Primary and secondary IgG responses equally recognized the epitopes of the TI-2 and TD immunogens, whereas IgM responses favored the TI-2 epitope. Because PAMPs alone can result in Abs to 2,4,6-triitrophenyl and FLU without immunization, it suggests they alone cause differentiation of B cells of the preimmune repertoire. The finding that both bacterial PAMPs and colonization are capable of stimulating Ab responses in both immunized and nonimmunized piglets suggests that PAMPs derived from host flora may play a major role in awakening adaptive immunity in neonates.

Antibody structural variation in rainbow trout fluids

Rainbow trout (Oncorhynchus mykiss) were immunized with trinitrophenylated-keyhole limpet hemocyanin (TNP-KLH) and the redox structure of induced anti-TNP antibodies from the serum, mucus, egg and ovarian fluid was examined. In conducting these studies it was determined that all TNP-specific antibody from each source possessed the mAb-specific H chain (1-14) epitopes, which facilitated the direct structural analysis of the induced antibodies. A protocol was developed which ensured complete adsorption of all specific anti-TNP antibody from each fluid. Together these protocols permitted the unbiased compositional analysis of all redox forms of the anti-TNP antibodies from each source. All antibodies, regardless of source, possessed the same molecular mass, characteristic of the trout tetramer (800 kDa). It was found that specific antibody titers were significantly higher in male than female trout, while the degree of disulfide polymerization was relatively invariant in male antibodies, while being highly variable in female antibodies. Within the females, no distinctively different redox ratios were between antibodies isolated from sera, ovarian fluid or eggs: however, mucus antibodies possessed a unique redox structure consisting of halfmeric constituents that were not observed in antibodies from other fluids.

Rapid induction of splenic and peritoneal B-1a cells in adult mice by thymus-independent type-2 antigen

We have produced a transgenic mouse (PV1TgL) that can only generate B lymphocytes with an Ig receptor specific for the synthetic polymer polyvinyl pyrrolidinone. Before immunization, bone marrow B cell numbers are very low, and peripheral lymphoid organs are almost devoid of B cells, confirming the role of positive selection by Ag in the development of mature B cell populations. The predominant population of B cells in the spleens of naive adult PV1TgL mice have most of the characteristics of marginal zone B cells, including anatomical location in the peripheral areas of the splenic white pulp. After immunization, a new population of B cells appears in the spleen with the characteristics of B-1 cells. Similar cells also appear somewhat later in the peritoneal cavity. Our findings suggest that immunization with a thymus-independent Ag can lead to the appearance and expansion of Ag-reactive B-1 cells in an adult mouse.

Scurfin (FoxP3) controls T-dependent immune responses in vivo through regulation of CD4+ T cell effector function

Scurfin, the protein product of the FoxP3 gene, is a forkhead-family transcription factor that negatively regulates T cell function. Mice carrying a loss-of-function mutation in FoxP3 (scurfy mice) present with fatal autoimmune-like disease caused by hyperresponsive CD4(+) T cells. Mice that overexpress scurfin (FoxP3 Tg mice) possess fewer mature T cells with reduced functional capabilities compared with normal littermate control mice. We analyzed the ability of CD4(+) T cells and B cells from FoxP3 Tg mice to respond to a T-dependent Ag and found that immunized FoxP3 Tg mice displayed reduced total and Ag-specific serum Ig and disorganized splenic architecture. However, when cultured in vitro, FoxP3 Tg B cells responded normally, suggesting that the poor Ab response was a result of defective T cell help in vivo. When challenged, CD4(+) T cells from FoxP3 Tg mice display reduced up-regulation of CD40 ligand and fewer IFN-gamma-producing cells. Overall, these findings show that overexpression of scurfin reduces T cell responses in vivo such that CD4(+) T cells cannot provide help to B cells during a T cell-dependent Ab response.

IKK beta is required for peripheral B cell survival and proliferation

NF-kappaB activity in mammalian cells is regulated through the IkappaB kinase (IKK) complex, consisting of two catalytic subunits (IKKalpha and IKKbeta) and a regulatory subunit (IKKgamma). Targeted deletion of Ikkbeta results in early embryonic lethality, thus complicating the examination of IKKbeta function in adult tissues. Here we describe the role of IKKbeta in B lymphocytes made possible by generation of a mouse strain that expresses a conditional Ikkbeta allele. We find that the loss of IKKbeta results in a dramatic reduction in all peripheral B cell subsets due to associated defects in cell survival. IKKbeta-deficient B cells are also impaired in mitogenic responses to LPS, anti-CD40, and anti-IgM, indicating a general defect in the ability to activate the canonical NF-kappaB signaling pathway. These findings are consistent with a failure to mount effective Ab responses to T cell-dependent and independent Ags. Thus, IKKbeta provides a requisite role in B cell activation and maintenance and thus is a key determinant of humoral immunity.

Architectural defects in the spleens of Nkx2-3-deficient mice are intrinsic and associated with defects in both B cell maturation and T cell-dependent immune responses

Mice lacking the homeodomain transcription factor Nkx2-3 are either asplenic or develop a spleen of significantly reduced size with poorly organized white pulp. In this report, we analyze the effect of this mutation on B lymphocyte development and differentiation. Follicular dendritic cells in spleen, but not lymph node, of Nkx2-3(-/-) mice fail to express a developmental Ag (follicular dendritic cell-M2) and show an abnormal association with B cells, despite essentially normal expression of several chemokine genes. Bone marrow reconstitution studies show the splenic disorganization and absence of marginal zone B cells to be of stromal rather than hemopoietic origin. Furthermore, Nkx2-3(-/-) mice show an excess of conventional B cells in mesenteric lymph node and peritoneal cavity, whereas transitional B cells are rare in spleen but overrepresented in bone marrow. Finally, immunization of Nkx2-3(-/-) mice with a T cell-dependent Ag elicits clusters of germinal center B cells, although these fail to develop to the same extent as in controls and there is no evidence of affinity maturation in serum Ab. Similarly, Ab-forming cells fail to aggregate into foci early in the response. Collectively, these data indicate a substantial role for Nkx2-3 in the correct association of lymphocytes and splenic stromal elements that is independent of chemokine expression.

The Yaa mutation promoting murine lupus causes defective development of marginal zone B cells

The accelerated development of systemic lupus erythematosus (SLE) in BXSB male mice is associated with the presence of an as yet unidentified mutant gene, Yaa (Y-linked autoimmune acceleration). In view of a possible role of marginal zone (MZ) B cells in murine SLE, we have explored whether the expression of the Yaa mutation affects the differentiation of MZ and follicular B cells, thereby implicating the acceleration of the disease. In this study, we show that both BXSB and C57BL/6 Yaa mice, including two different substrains of BXSB Yaa males that are protected from SLE, displayed an impaired development of MZ B cells early in life. Studies in bone marrow chimeras revealed that the loss of MZ B cells resulted from a defect intrinsic to B cells expressing the Yaa mutation. The lack of selective expansion of MZ B cells in diseased BXSB Yaa males strongly argues against a major role of MZ B cells in the generation of pathogenic autoantibodies in the BXSB model of SLE. Furthermore, a comparative analysis with mice deficient in CD22 or expressing an IgM anti-trinitrophenyl/DNA transgene suggests that the hyperreactive phenotype of Yaa B cells, as judged by a markedly increased spontaneous IgM secretion, is likely to contribute to the enhanced maturation toward follicular B cells and the block in the MZ B cell generation.

B cell developmental requirement for the G alpha i2 gene

Null mutation of the Galphai2 trimeric G protein results in a discrete and profound mucosal disorder, including inflammatory bowel disease (IBD), attenuation of IL-10 expression, and immune function polarized to Th1 activity. Genetic and adoptive transfer experiments have established a role for B cells and IL-10 in mucosal immunologic homeostasis and IBD resistance. In this study, we addressed the hypothesis that Galphai2 is required for the development of IL-10-producing B cells. Galphai2(-/-) mice were reduced in the relative abundance of marginal zone (MZ), transitional type 2 (T2), and B-1a B cells and significantly increased in follicular mature and B-1b B cells. Reconstitution of RAG2(-/-) mice with Galphai2(-/-) bone marrow induced an IBD-like colitis and a deficiency in absolute numbers of MZ, T2, and B-1 B cells. Thus, the Galphai2(-/-) genotype in colitis susceptibility and B cell development involved a cis effect within the hemopoietic compartment. In vitro, the B cell population of Galphai2(-/-) mice was functionally deficient in LPS-induced proliferation and IL-10 production, consistent with the exclusive capacity of T2 and MZ cell subpopulations for LPS responsiveness. In vivo, Galphai2(-/-) mice were selectively impaired for the IgM response to T-independent type II, consistent with the relative depletion of MZ and peritoneal B-1 subpopulations. Collectively, these results reveal a selective role for Galphai2 in MZ and B-1 B cell development. Disorders of this Galphai2-dependent process in B cell development may represent a mechanism for IBD susceptibility.

Differential requirements for expression of CD80/86 and CD40 on B cells for T-dependent antibody responses in vivo

The CD80/86-CD28 and CD40-CD40 ligand costimulatory pathways are essential for Th cell-dependent B cell responses that generate high-affinity, class-switched Ab in vivo. Disruption of either costimulatory pathway results in defective in vivo humoral immune responses, but it remains unclear to what extent this is due to deficient activation of Th cells and/or of B cells. To address this issue, we generated mixed chimeras in which CD80/86- or CD40-deficient bone marrow-derived cells coexist with wild-type (WT) cells, thereby providing the functional T cell help and accessory cell functions required for fully competent B cell responses. We were then able to assess the requirement for CD80/86 or CD40 expression on B cells producing class-switched Ig in response to a T-dependent Ag. In CD80/86 WT plus CD80/86 double-knockout mixed chimeras, both WT- and CD80/86-deficient B cells produced IgG1 and IgE responses, indicating that direct signaling by CD80/86 is not essential for efficient B cell activation. In marked contrast, only WT IgG1 and IgE responses were detected in the chimeras containing CD40-deficient cells, demonstrating that CD40 expression on B cells is essential for class switching by those B cells. Thus, while disrupting either the CD80/86-CD28 or the CD40-CD40 ligand costimulatory pathway abrogates T-dependent B cell immune responses, the two pathways are nonredundant and mediated by distinct mechanisms.

Antibody repertoire development in fetal and neonatal piglets. VIII. Colonization is required for newborn piglets to make serum antibodies to T-dependent and type 2 T-independent antigens

Cesarean-derived piglets were reared for 5 wk under germfree conditions or monoassociated with a benign Escherichia coli (G58-1) or a enterohemorrhagic strain (933D) derived from O157:H7, and immunized i.p. with the T-dependent (TD) Ags fluorescein-labeled (FL) keyhole limpet hemocyanin or trinitrophenylated (TNP) keyhole limpet hemocyanin and the type 2 T-independent Ags TNP-Ficoll or FL-Ficoll. Only colonized piglets showed an increase in serum IgG, IgA, and IgM and had serum Abs to FL, TNP, and colonizing bacteria. While serum Abs to FL or TNP appeared following colonization alone, secondary responses were restricted to piglets immunized using TD carriers. While animals colonized with 933D had significantly higher total serum IgG and IgM levels and specific IgG Abs than those colonized with G58-1, no differences were seen in serum IgA levels, B cell diversification in the ileal Peyer's patches, and specific activity (ELISA activity per micrograms of Ig) of pre-boost serum IgG and IgM anti-TNP and anti-FL Abs. Serum IgA Abs to TNP, FL, or bacteria were not detected. Ag-driven responses, as measured by an increase in specific Ab activity, were only observed in secondary responses to TD Ags and to colonizing, pathogenic E. coli. We propose that germline-encoded, isotype-switched B cells in newborn piglets differentiate to Ab-secreting cells 1) after stimulation by bacteria-activated APCs or 2) through direct stimulation by bacterial products. We further propose that Ag-driven systemic responses require both bacterial colonization and TD Ags translocated to the peritoneum.

The absence of Tssc6, a member of the tetraspanin superfamily, does not affect lymphoid development but enhances in vitro T-cell proliferative responses

The tetraspanins are a family of integral membrane proteins with four transmembrane domains. These molecules form multimolecular networks on the surfaces of many different cell types. Gene-targeting studies have revealed a role for tetraspanins in B- and T-lymphocyte function. We have isolated and deleted a novel tetraspanin, Tssc6, which is expressed exclusively in hematopoietic and lymphoid organs. Using a gene-trapping strategy, we generated an embryonic stem (ES) cell line with an insertion in the Tssc6 locus. Mice were derived from these ES cells and, using RNase protection and reverse transcription-PCR, we demonstrated that the insertion resulted in a null mutation of the Tssc6 allele. Mice homozygous for the gene trap insertion (Tssc6(gt/gt) mice) were viable and fertile, with normal steady-state hematopoiesis. Furthermore, responses to hemolysis and granulocyte colony-stimulating factor-induced granulopoiesis were equivalent to those of wild-type mice. Lymphoid development was normal in Tssc6(gt/gt) mice. Whereas Tssc6(gt/gt) B cells responded normally to lipopolysaccharide, anti-CD40, and anti-immunoglobulin M stimulation, Tssc6(gt/gt) T cells showed enhanced responses to concanavalin A, anti-CD3, and anti-CD28. This increased proliferation by Tssc6-deleted T lymphocytes was due to increased interleukin 2 production following T-cell receptor stimulation. These results demonstrate that Tssc6 is not required for normal development of the hematopoietic system but may play a role in the negative regulation of peripheral T-lymphocyte proliferation.

Low-level hypermutation in T cell-independent germinal centers compared with high mutation rates associated with T cell-dependent germinal centers

Exceptionally germinal center formation can be induced without T cell help by polysaccharide-based antigens, but these germinal centers involute by massive B cell apoptosis at the time centrocyte selection starts. This study investigates whether B cells in germinal centers induced by the T cell-independent antigen (4-hydroxy-3-nitrophenyl)acetyl (NP) conjugated to Ficoll undergo hypermutation in their immunoglobulin V region genes. Positive controls are provided by comparing germinal centers at the same stage of development in carrier-primed mice immunized with a T cell-dependent antigen: NP protein conjugate. False positive results from background germinal centers and false negatives from non-B cells in germinal centers were avoided by transferring B cells with a transgenic B cell receptor into congenic controls not carrying the transgene. By 4 d after immunization, hypermutation was well advanced in the T cell-dependent germinal centers. By contrast, the mutation rate for T cell-independent germinal centers was low, but significantly higher than in NP-specific B cells from nonimmunized transgenic mice. Interestingly, a similar rate of mutation was seen in extrafollicular plasma cells at this stage. It is concluded that efficient activation of hypermutation depends on interaction with T cells, but some hypermutation may be induced without such signals, even outside germinal centers.

Accessory cell defect in unresponsiveness of neonates and aged to polysaccharide vaccines

T independent antigens elicit antibody responses in the absence of carrier specific T helper cells but require signals from accessory cells (macrophages and dendritic cells) or specific cytokines. They are further subdivided into TI-1 and TI-2 categories based on the ability of TI-1 but not TI-2 antigens to elicit immune responses from neonates. Most bacterial polysaccharides including the pneumococcal polysaccharide vaccines belong to the TI-2 class. It is hypothesized that defects in accessory cell function play a critical role in the failure of neonates to respond to such TI-2 antigens. Immune responses to these TI-2 stimuli are also reduced in the aged, also due to a quantitative deficiency in accessory cells. Agents that can stimulate accessory cell function may provide an alternative strategy to improve the immunogenicity of the polysaccharide vaccines in the neonates and the aged.

Carrier-induced, hapten-specific suppression: a problem of antigen presentation?

Prior immunity against a carrier protein has been shown to modulate the serologic response to injected haptens attached to the same carrier. In particular, a carrier/hapten-carrier immunization protocol induces marked suppression for IgG2a anti-hapten Ab production but does not interfere with anti-carrier Ab responses. Although the phenomenon of epitopic suppression has been amply demonstrated, the mechanism underlying the suppression remains unknown. The selective deficiency in IgG2a secretion suggests that IFN-gamma-producing Th1 cells are not properly activated. We and others have shown that the nature of the APCs present during the first encounter with the Ag influences the development of selected Th populations in vivo; dendritic cells (DCs) seem to be required for the induction of primary, Th1-type responses. Since carrier priming induces the clonal expansion of specific B cells that appear to efficiently capture the Ag, we hypothesized that the hapten-carrier conjugate may be presented by B cells in preimmunized animals. Therefore, we immunized mice to the conjugate by injecting syngeneic DCs pulsed in vitro with the Ag. Our data show that an injection of DCs and IL-12 prevents epitopic suppression, suggesting that it may result from defective Ag presentation.

Acute and long-term effects of stressors on pulmonary immune functions

To study the effects of different types or intensities of stressors on immune reactivity in the lungs, we studied the ex vivo production of nitric oxide (NO) and IL-1beta by alveolar macrophages (AM) after short exposure of rats to restraint stress or inescapable electric footshocks. Exposure to electric footshocks of various intensities resulted in an intensity-dependent decrease in NO production whereas the IL-1beta production by AM had increased. The secretory activity was similarly affected by restraint stress. When the time course of electric footshocks on secretory functions of AM was studied, it was found that the effects on NO and IL-1beta production by AM were normalized 3 days after the stress induction, but reappeared when cells were isolated 1 to 2 wk after stress exposure. Analysis of the effects of electric footshocks of various intensities on antibody production 10 days after the stress session and subsequent lung immunization with trinitrophenyl conjugated keyhole limpet hemocyanin (TNP-KLH), showed a footshock intensity-dependent response. Although exposure to stress induced an increase in plasma levels of adrenocorticotropic hormone (ACTH) and corticosterone (CORT), hormone levels did not differ between the various stress-exposed groups. This suggests that the observed stress effects on pulmonary immune functions were not mediated by ACTH or CORT but point to a direct involvement of the autonomic nervous system.

Repeated high dose oral exposure or continuous subcutaneous infusion of 2-methoxyacetic acid does not suppress humoral immunity in the mouse

2-Methoxyethanol (ME) has been shown to be immunosuppressive in rats but not mice, with oxidation of ME to 2-methoxyacetic acid (MAA) being a prerequisite for immunosuppression. MAA is more rapidly cleared by mice than rats, consequently this study was designed to determine if increasing the bioavailability of MAA in mice might play a role in this species difference. Female B6C3F1 mice were given MAA by oral multiple daily high doses or by continuous subcutaneous infusion via mini-osmotic pumps. Humoral immunity was evaluated in MAA-exposed mice using the plaque-forming cell (PFC) response to either sheep red blood cells (SRBC) or trinitrophenyl-lipopolysaccharide (TNP-LPS). Female F344 rats were also used to compare the effects of multiple daily MAA exposure on these humoral immune responses. Rats and mice were dosed orally twice a day for 4 days by gavage with MAA at dosages ranging from 40-320 mg/kg/day and 240-1920 mg/kg/day, respectively. All animals were immunized on the first day of dosing and body and lymphoid organ weights and PFC responses to SRBC or TNP-LPS were evaluated 4 days later. While body weights in rats were unaffected, thymus weights were reduced at all dosages of MAA and spleen weights were reduced at 160 or 320 mg/kg/day. PFC responses to SRBC and TNP-LPS were suppressed in rats at dosages of 160 and 320 mg/kg/day. In contrast, thymus weights of mice were reduced only at 960 mg/kg/day or greater, with no effect on spleen or body weights. Furthermore, neither the PFC response to SRBC nor the response to TNP-LPS was suppressed in mice exposed to any oral dosage of MAA. In the continuous infusion study, mice were subcutaneously implanted with mini-osmotic pumps containing MAA which was delivered at 840 mg/kg/day over a 7-day period. Continuous exposure to MAA via mini-osmotic pumps did not suppress the PFC response to either SRBC or TNP-LPS, but rather significantly enhanced the response to TNP-LPS. These results indicate that mice are insensitive to MAA even at the high dosages given as a bolus or continuously over 1 week. The data further support earlier work, which suggested that the observed difference between rats and mice for MAA-induced immunosuppression appears to be unrelated to the availability of MAA to target lymphoid tissue in these rodent species.

Liposomes that provide T-dependent help to weak antigens (T-independent antigens)

The design of an adjuvant for eliciting a thymus-dependent response to LPS, a well-defined thymus-independent antigen, is presented. Hybrid liposomes containing LPS and HA2 peptide from the hemagglutinin protein of influenza virus within the liposome bilayer were prepared (LPS/HA2 liposomes). The HA2 polypeptide contains epitopes recognized by T-helper lymphocytes and T-cytotoxic lymphocytes. Outbred mice immunized with LPS/HA2 liposomes produced anti-LPS-specific IgG responses. IgG subclass analysis indicated that IgG1, IgG2, and IgG3 antibodies were produced by these animals. LPS liposomes (liposomes without HA2) stimulated a T-independent response only. This was demonstrated by the detection of IgG3 but not IgG1 or IgG2 in serum of mice immunized with LPS liposomes. These results support the concept that the simultaneous incorporation into liposomes of a polypeptide with T-cell recognition sites along with a T-independent antigen can lead to the generation of cognate T-cell help for the T-independent antigen. The synthesis and characterization of a neo-lipopolysaccharide T-independent antigen for incorporation in hybrid HA2 liposomes are also presented. Findings are discussed relative to the liposome model used and implications for development of vaccines for use in humans.

The thymus-independent antigen alpha(1-3) dextran elicits proliferation of precursors for specific IgM antibody-producing cells (memory cells), which are revealed by LPS stimulation in soft agar cultures and detected by immunoblot

Single antibody-forming cells (AFC) specific for alpha(1-3) dextran (Dex) from i.p.-immunized BALB/c mice were enumerated in soft agar cultures by blotting on antigen-precoated membranes and subsequent staining via enzyme-coupled anti-IgM antibodies. Short cultures (2 h) revealed AFC as harvested ex vivo, while in long-term cultures (4 days), in the presence of lipopolysaccharide (LPS) as B cell mitogen, cells or colonies developed by differentiation in vitro. Whereas the spleen contained most AFC ex vivo in a sharp-peak response at 4 and 5 days after i.p. injection of Dex in aqueous solution, peritoneal exudate cells (PEC) contained only very few AFC. However, the same PEC population developed Dex-specific cells or colonies after 4 days of culture. The isotype of antibodies was IgM. The frequency of these Dex-specific LPS-inducible precursor cells rose exponentially in the course of the immune response to a broad plateau and was still, 11 weeks after Dex injection, approximately 40-fold higher than in non-immunized mice. Since these cells increased in frequency after antigen injection, and since they could not be detected as AFC during 2 h ex vivo, they were regarded as memory cells. They seemed to be arrested in vivo, but could be induced to differentiation and/or proliferation in vitro. Although these cells had the functional characteristics of memory cells as defined above, they produced anti-Dex antibodies of IgM isotype. Their population might be critical for the protection of the peritoneal cavity against microbial invasion from the intestines, and it may be significant in this context that we could evoke a peritoneal memory cell response only when antigen was injected intraperitoneally, but not intravenously. In athymic BALB/c-nu/nu mice only few of these Dex-specific memory cells were found. It is possible that T cells exert a regulatory influence on this pathway of differentiation.

Rational design of conjugate vaccines

Whereas bacterial polysaccharides, classified as T-cell-independent antigens, elicit protective antibodies in adults, booster injections fail to produce an augmented response or promote antibody class switching. Because T-cell-dependent antigens, typically proteins, both produce boosted antibody levels and promote antibody class switching, it has been considered highly desirable to attempt to convert the T-cell-independent polysaccharide antigens into T-cell-dependent antigens, particularly for use in high-risk groups. A number of clinical trials now report the efficacy of conjugate vaccines in inducing the production of antibody in response to a number of previously poorly immunogenic--mainly T-cell-independent--antigens. In addition to conjugate vaccines containing bacterial polysaccharides, vaccines containing relevant peptides from a variety of pathogens are also being formulated and investigated. Questions remain, however, regarding their synthesis, use, and efficacy. The best ages for vaccine administration and selection of the optimal protein carrier are still under investigation, as are questions regarding the use of adjuvants, which can greatly affect the vaccine's potency. Spacing and size of epitope and size and composition of the final structure also must be considered; the importance of molecular size and aggregation of antigen in increasing immunogenicity have been well documented. These questions must be addressed for the much-needed development of conjugate vaccines against some common infections worldwide, including malaria, bacterial meningitis, and infections from Pseudomonas aeruginosa and Neisseria gonorrhoeae because of increasing susceptibility to these infections and resistance of the pathogens to chemotherapeutic agents and/or antibiotics.

Effects of route of immunization, adjuvant and unrelated antigens on the humoral immune response in lines of chickens selected for antibody production against sheep erythrocytes

Effects of intramuscular (i.m.), intravenous (i.v.) and intraperitoneal (i.p.) primary immunization with the T-dependent antigen, sheep red blood cells (SRBC), was studied in two chicken lines selected for either high (H) or low (L) antibody response after i.m. immunization with SRBC. The primary route of immunization affected the line differences in the primary response and in the secondary response after i.m. reimmunization. Intravenous immunization with the T-dependent antigen bovine serum albumin (BSA) showed line differences similar to those found after i.m. or i.v. immunization with SRBC. Immunization with both the partially T-independent antigens Brucella abortus (BA) or Salmonella H-antigen (SHA) revealed no line effect. Immunization with SRBC in incomplete Freund's adjuvant (IFA) did not change the difference between lines, whereas immunization with complete Freund's adjuvant (CFA) diminished the difference between lines. It is postulated that differences in antibody production between the selected lines might be attributed to differences in T-cell activity.

A purified saponin acts as an adjuvant for a T-independent antigen

Three strains of mice were injected with a T-independent antigen, Escherichia coli 055:B5 polysaccharide (PS) combined with purified saponin, QS-21, isolated from Quillaja saponaria bank. PS was prepared by hydrolysis of lipopolysaccharide (LPS). Nine week old mice were injected intradermally with 60 micrograms PS, as determined by an anthrone assay, with or without 15 micrograms QS-21 on days 0 and 14. On day 22 sera were assayed by EIA for PS specific antibodies. Titers were 11-fold higher in CD-1 mice with QS-21. C3H/HeJ (Ipsd) and C3H/HeSnJ (Ipsr) mice also showed an adjuvant associated increase in titer with saponin. Therefore, LPS responsiveness was not required for the adjuvant effect. PS vaccinated C3H and CD-1 mice with and without QS-21 had similar antibody isotype profiles. IgG2b titers accounted for more than half of the total Ig response. IgG2a was next highest followed by IgG3, IgM, IgG1, and IgA. In comparison, CD-1 mice injected with 0.1 microgram intact LPS had a different LPS specific isotype profile. IgG3 was the highest followed by IgG1, IgG2b, IgM, IgG2a, and IgA.

Neonatal suppression with anti-Ia antibody. III. In vivo responses to the type 2 antigen TNP-Ficoll

We studied the response to thymus-independent type 2 (type 2) Ag in mice suppressed from birth with anti-Ia antibody. Although these mice have significantly reduced numbers of surface IgM+ cells and reduced or absent levels of Ia-restricted Th cell activity, their IgM antibody response to the type 2 Ag TNP-Ficoll was unaffected whereas that to the prototypic thymus-dependent Ag SRBC was predictably eliminated. These data suggest that an in vivo antibody response can be made to type 2 Ag in the absence of Ia-dependent cellular interactions. The surface IgM+IgD-Ia- B cells that are found in the anti-Ia antibody-suppressed mouse may represent an expanded population of Ia-independent, type 2 Ag-sensitive B cells normally present as a smaller proportion of the splenic lymphocyte population. Thymus-dependent responses, which have been shown to have an absolute requirement for an Ia-dependent interaction, are absent in these animals.

Antibody responses to hapten in thymectomized mice: extraordinarily pronounced deficiency in IgG1 production

The effect of thymectomy on the production of antibodies was studied by immunizing mice with hapten-carrier conjugates. Antibody responses were analysed with monoclonal antibody-based quantitative isotype-resolving assays. In spite of bone marrow reconstitution, irradiation without thymectomy caused a long-lasting relative deficiency in responsiveness to T-independent antigens. Even when no visible remnants of the thymus could be observed at the autopsy of thymectomized mice, there appeared to be a gradual recovery of antibody-forming capacity within 4 months, as assessed by the response to a T-dependent antigen. Therefore, some of the thymectomized mice had to be regarded as having recovered with respect to the helper T-cell effect. The antibody responses to T-dependent antigens were improved in all isotypes by a functional T-cell system, but the IgG isotypes seemed to benefit more than IgM. The most conspicuous deficit in antibody production in non-recovered thymectomized mice was observed in the T-dependent responses of the IgG1 isotype (2000-fold reduction in contrast to about 50- to 100-fold in IgG2a, IgG2b, and IgG3).

Primary in situ immune response in popliteal lymph nodes and spleen of mice after subcutaneous immunization with thymus-dependent or thymus-independent (type 1 and 2) antigens

Mice were immunized subcutaneously with thymus-independent (TI)-type 1 antigen trinitrophenylated lipopolysaccharide (TNP-LPS), TI-type 2 antigen TNP-Ficoll or thymus-dependent (TD) antigen TNP-keyhole limpet haemocyanin (TNP-KLH) in order to study the primary in situ immune response in popliteal lymph nodes (PLN) and spleen. The spleen responded more rapidly in developing specific antibody-forming cells (AFC) than the lymph nodes did, in spite of the fact that antigens reach the spleen only after passing several lymph node stations. This difference between lymph nodes and spleen in developing AFC was particularly significant with respect to the responses to TI (both type 1 and type 2) antigens. No differences in the distribution of specific AFC in PLN and spleen were observed after immunization with TI and TD antigens. Results are discussed with respect to the relative contributions of lymph nodes and spleen to immune responses to antigens injected subcutaneously.

Aging effects on secretory IgA immune responses

Studies of cellular and humoral components of the secretory immune system indicated dramatic decreases in the SIgA response to T-dependent antigens (i.e. DNP-BGG) in aged rats. Senescent rats (18-20 months old) showed comparable levels of SIgA anti-DNP antibody to adult animals after oral immunization with a T-independent antigen, DNP-FICOLL. The salivary SIgA responses to both antigens were substantially decreased in weanling rats (21-35 days) versus the adult rats. Significant anamnestic SIgA responses were shown after oral immunization with DNP-BGG in adult rats, but was not observed in the senescent and midlife (10-12 months) rats. In contrast, the DNP-FICOLL appeared incapable of eliciting a secondary SIgA response in any of the groups. Examination of immunoglobulin-containing cells (ICC) in secretory and lymphoid tissues indicated a generally decreased proportion of IgAICC and IgGICC in the secretory tissues from the senescent rats. IgAICC and IgGICC were within normal limits in the lymphoid tissues of the senescent rats. The results demonstrate a defect in the ability of aged rats to manifest an IgA response to T-dependent antigens administered at mucosal surfaces.

Immune memory expression to Tnp-Ficoll in CB.20 mice: evidence for a multigenic control

Trinitrophenyl (Tnp)-Ficoll, a class 2 thymus-independent (TI) antigen, generates in most mouse strains Tnp-specific B-memory cells which can be detected in situ 1 week after priming by a heterologous stimulation with Tnp-lipopolysaccharide (LPS) but not by a homologous Tnp-Ficoll challenge. We have investigated the secondary responses raised in CB.20 congenic mice by a homologous challenge in situ occurring at various time intervals after priming. We report that a memory-type response is obtained, culminating when the challenge is performed at 4 weeks; this finding assesses definitely the ability of TI-2 antigens to produce immunological memory under standard conditions. However, the same immunization procedure elicits no memory-type response in the majority of other mouse strains, suggesting a possible genetic control of the expression of memory to class 2 TI antigens. The utilization of F1 hybrids between C57BL/6 and BALB/c and of appropriate congenic strains shows indeed that this memory expression is under multigenic control: Igh-V or closely linked genes are clearly involved but a complementation with other gene(s), located outside the H-2 complex, is required for a memory-type response to Tnp-Ficoll. We have also analyzed the secondary heterologous response to Tnp-LPS in CB.20 mice at different times after Tnp-Ficoll priming. The difference in the kinetic profile of the heterologous (TI-2----TI-1) versus homologous (TI-2----TI-2) secondary responses is discussed in terms of B-memory-cell ontogeny and humoral regulation.

Physiology of IgD. V. Enhancement of antibody responses in vivo by allo anti-IgD is due primarily to an indirect effect on B cells

Although responses of BALB/c mice to TNP-Ficoll or TNP-Brucella abortus are usually decreased by injection of allo anti-IgD (anti-Igh-5a) given 1 day before antigen, increased responses are obtained if a lymphokine mixture (SN) containing IL 2 is also injected. Simultaneous injection of anti-IgD and SN 4 days after priming with TNP-KLH induces an increase in antibody production similar to that induced by a second antigen injection. Injected together with a second injection of TNP-KLH at that time, anti-IgD and SN cause a synergistic enhancement of the secondary response. In allotype heterozygous (BALB/c X SJL)F1 mice injected with anti-IgD directed against one allotype, this enhancement of the secondary response is seen predominantly in the alternate allotype, because the IgG response of linked allotype specificity is slightly suppressed by the anti-IgD alone and is less enhanced than the alternate allotype by anti-IgD plus SN. Cells from unprimed heterozygous mice, incubated with anti-Igh-5a in vitro and transferred, together with antigen, to TNP-KLH-primed recipients, cause a much greater enhancement of the IgG responses of the Igb than of the Iga allotype in recipients. If, however, SN is also injected into the recipients, the anti-TNP response of both IgG allotypes is greatly enhanced.

Hormonal modulation of responses to thymus-independent and thymus-dependent antigens in autoimmune NZB/W mice

Previous work suggested that gonadal steroids influence immunity through the thymus, but the mechanisms were unclear. To investigate the effects of these hormones on immune responses to T1 and TD antigens in autoimmune mice, we studied hybrid NZB/W mice and the nonautoimmune DBA/2 strain. Mice castrated at 14 days of age were implanted with Silastic capsules releasing, in adults, physiologic levels of E2 in males or Te in females. Sham-operated controls received empty capsules. Splenic PFC were quantified 4 to 5 days after challenge with the TI2 antigen TNP-Ficoll, the TI1 antigen TNP-LPS, or the TD antigen SRBC. Young castrated NZB/W males implanted with E2 had striking enhancement of IgM responses to TNP-Ficoll when compared to castrated Te-treated females and comparable sham-operated controls of both sexes. E2 also stimulated responses to TNP-LPS. In response to challenge with SRBC, young E2-treated NZB/W males had a consistent trend to increased IgM PFC, and the stimulatory effect of E2 on IgG plaques was variable. Physiologic doses of Te had no consistent effect on responses in young mice. In old female NZB/W mice, Te caused PFC response after immunization with TNP-Ficoll to resemble age-matched NZB/W males. As sham-operated NZB/W females grew older, PFC responses to SRBC fell. This age-related phenomenon was delayed, however, in female castrates implanted with Te. In contrast, Te clearly suppressed responses to TNP-LPS. Implantation of E2 did not alter responses to TNP-Ficoll, TNP-LPS, or SRBC in nonautoimmune DBA/2 males. This finding suggested that exogenous E2 given in physiologic doses did not influence immunologic responsiveness in a normal strain to the degree seen in hormone-sensitive NZB/W mice. It was concluded that E2 enhanced responses to a variety of exogenous antigens in autoimmune NZB/W mice. The most consistent E2-induced increase in PFC response was observed with TI antigens, suggesting that E2 exerted its effects on B cells or Ts.

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.

Selective effect of irradiation on responses to thymus-independent antigen

Low doses of ionizing radiation have a selective immunosuppressive effect on in vivo B cell responses to thymus-independent (TI) antigens. The B cell response, assayed as direct anti-trinitrophenyl (TNP)-specific plaque-forming cells (PFC), induced by type 2, TI antigens (TNP-Ficoll or TNP-Dextran), was reduced, on the average, by 10-fold in animals exposed to 200 rad of ionizing radiation 24 hr before antigen challenge. In contrast, PFC responses to type 1, TI antigens (TNP-lipopolysaccharide or TNP-Brucella abortus) are unaffected in mice exposed to the same dose of radiation. Adoptive transfers showed that this selective immunosuppression is a result of the specific inactivation of the B cell subpopulation responding to type 2, TI antigens. These experiments suggest that physiologic differences exist in the B cell subpopulations of normal mice which respond to type 1, or type 2, TI antigens.

Preferential induction of specific lambda-isotypic antibodies in mice

A high proportion (greater than 40%) of lambda-anti-NP antibodies were induced after the administration of hapten conjugates of the relatively T-independent antigen NP-Ficoll. In 11 of 12 strains, lambda 1 anti-NP antibodies were the predominant isotype. In lambda 1-defective SJL mice, lambda 2,3 anti-NP antibodies were the major species after NP-Ficoll immunization. In contrast, the ability to elicit a high proportion of lambda-anti-NP antibodies with the T-dependent conjugate of ovalbumin, NP-OVA, varied among mouse strains. Igh-1b-bearing mice were high producers of lambda 1 anti-NP antibodies (greater than 70% of the response); DBA/2 and BALB/c mice were moderate (40 to 50%) lambda 1 anti-NP producers, and A.TL, AKR, NZB, and C3H mice were low lambda 1 anti-NP producers (less than 10%) after primary NP-OVA immunization. In the latter group, NP-OVA preferentially elicits kappa-bearing anti-NP antibodies. The parameters that influence the distribution of light chain isotypes were investigated. The preferential induction of lambda-anti-NP antibodies with NP-Ficoll was a) partially influenced by Igh-linked genes, b) adjuvant independent, and c) maintained on prolonged immunization. In contrast, induction of a high proportion of kappa-anti-NP antibodies by NP-OVA is (a) strictly regulated by Igh-linked genes and (b) enhanced after hyperimmunization. The immunochemical, genetic, and cellular bases for these observations are discussed.

Effects of deoxycoformycin in mice. I. Suppression and enhancement of in vivo antibody responses to thymus-dependent and -independent antigens

The effect of 2'-deoxycoformycin (DCF) on the PFC responses of AKR mice to SE, TNP-Ficoll, and TNP-B. abortus was examined. Subcutaneous injection of DCF 4 days before antigen caused suppression of all three responses by 70 to 78%. In contrast, injection of DCF 1 day after antigen caused enhancement of both the anti-SE and the anti-TNP-Ficoll responses. Although a single high dose of cortisone acetate injected 4 days before antigen caused a similar suppression, the effect of DCF was not mediated via a steroid release, inasmuch as DCF also suppressed the immune response in adrenalectomized mice. The response of BALB/c mice to TNP-Ficoll was also inhibited by DCF pretreatment and enhanced by injection of DCF after antigen. In contrast, in athymic mice DCF caused suppression of the anti-TNP-Ficoll PFC response, whether injected before or after antigen. These results are interpreted as suggesting that DCF causes suppression primarily via an effect on B cells. The enhancement seen in normal but not in athymic mice may possibly be ascribed to an effect on suppressor T cells. Apparently the enhancement of both TD and TI responses caused by DCF injected 1 day after antigen in normal mice is the net result of these two opposing effects. The results imply that helper T cells are resistant to DCF.

Opposite effects of total lymphoid irradiation on T cell-dependent and T cell-independent antibody responses

The effect of total lymphoid irradiation (TLI) on the primary antibody response to the dinitrophenylated heterologous protein, keyhole limpet hemocyanin (DNP-KLH), in complete Freund's adjuvant (CFA), and to the trinitrophenylated polysaccharide antigen, Brucella abortus (TNP-BA), was studied in BALB/c mice. The antibody response to both antigens was diminished in comparison with nonirradiated mice when antigens were injected within 3 days after TLI. When the mice were immunized 30 days after completion of TLI the antibody response to DNP-KLH in CFA was still diminished, but the antibody response to TNP-BA was enhanced 5- to 10-fold as compared with that of control animals. The opposite effect of TLI on the two antibody responses was also observed in a syngeneic primary adoptive transfer system.

Heterogeneous and monoclonal helper T cells induce similar anti-(4-hydroxy-3-nitrophenyl)acetyl (NP) antibody populations in the primary adoptive response. I. Isotype distribution

In the response to NP-lipopolysaccharide or NP-Ficoll predominantly anti-NP antibodies of the IgM class are produced in mice with lower amounts of IgG3 and IgG2b but little or no IgG1 and IgG2a. In contrast, in the primary T-dependent response to NP-keyhole limpet hemocyanin (KLH) or NP-chicken gamma globulin high amounts of all IgG isotypes are induced. To investigate whether isotype-specific T cells are responsible for these differences we carried out cell transfer experiments using carrier-specific T cell lines. Two such lines were established and one of the two could be cloned. Upon activation by antigen the T cell lines induced unprimed syngeneic splenic B cells to proliferate and differentiate into antibody-secreting cells in vitro in an antigen-nonspecific way. Antigen-specific activation of unprimed B cells in a cell transfer system in vivo showed that high concentrations of hapten-specific antibodies of all IgG isotypes are induced through both carrier-specific T helper lines. The isotypic pattern of these antibodies is similar to that produced via heterogeneous splenic T cells in the cell transfer system, or in normal animals on immunization with the same antigen. These results suggest that isotype-specific T cells are not required for the production of IgG isotypes in a primary anti-NP response and thus not responsible for the differences seen in isotypic patterns between T-dependent and T-independent responses.

Selective suppression by auto-anti-idiotypic antibody of B-cell idiotype repertoires generated after stimulation with the same hapten on T-dependent and T-independent carriers

In the present study, we investigated whether auto-anti-idiotypic antibody in the immune sera from old mice could recognize antitrinitrophenyl (TNP) plaque-forming cells (PFC) generated after stimulation with the T-dependent and T-independent forms of the hapten, TNP. Young and old C57BL/6J male mice were immunized with a variety of T-dependent (TNP-bovine gamma-globulin, TNP-BGG; TNP-keyhole Limpet hemocyanin, TNP-KLH; ovalbumin, OVA; bovine serum albumin, BSA; BGG) and T-independent (TNP-Brucella abortus, TNP-BA; TBP-Ficoll; TNP-polyacrylamide beads, TNP-PAA) antigens either in complete Freund's adjuvant (CFA) or in soluble form. Splenic anti-TNP or antiprotein PFC responses were assayed for anti-idiotype-blocked, hapten- or protein-augmentable IgM, IgG and IgA PFC, 1-2 weeks after immunization. It was found that 8-month-old mice produced significantly a higher percentage of hapten augmentable (26-42%) IgM PFC response to T-independent antigens as compared with the 2-month-old mice (3-6% augmentation). Similarly, old mice produced a significantly higher percentage of hapten or protein augmentable (25-129%) IgG PFC response to T-dependent antigens as compared with the 2-month-old group (2-6% augmentation). The data support the view that age-related regulation of auto-anti-idiotypic antibody is a general phenomenon for immune responses to T-dependent and T-independent antigens. Hapten-reversible inhibition of plaque formation was used to determine whether anti-idiotypic antibody containing antisera from old mice could inhibit B-cell idiotype repertoires generated after stimulation with the same hapten, TNP, on T-dependent and T-independent carriers. Pools of immune sera from 8-month-old mice primed with T-dependent TNP-BGG or TNP-KLH antigens but not with T-independent TNP-PAA or TNP-BA antigens, or with the proteins OVA, BSA, or BGG selectively inhibited IgM, IgG, and IgA anti-TNP PFC from 2-month-old mice that were previously primed with either TNP-BGG or TNP-KLH. In contrast, immune sera from old mice primed with TNP on either T-dependent or T-independent carriers inhibited anti-TNP PFC from mice primed with T-independent TNP-PAA or TNP-BA antigens. Immune sera from old mice primed with OVA or BSA only inhibited the respective antiprotein PFC. The immune sera from young mice did not show any appreciable inhibition of PFC generated after stimulation by any of the antigens studied.(ABSTRACT TRUNCATED AT 400 WORDS)

Lack of general immunosuppression during visceral Leishmania tropica infection in BALB/c mice: augmented antibody response to thymus-independent antigens and polyclonal activation

Leishmania tropica causes a lethal visceral disease in highly susceptible BALB/c mice, with many immunopathologic features resembling those in human kala-azar. The responses to thymus-independent antigens of Type 1 and 2 (TI-1, TI-2) were compared in infected mice of susceptible BALB/c and resistant C57BL/6 strains at various times after infection. The infected BALB/c mice had an augmented response to both types of antigens at 45 days after infection. Later (day 76), the response to trinitrophenylated lipopolysaccharide (TNP-LPS, a TI-1 antigen) was diminished but that to dinitrophenylated Ficoll (DNP-Ficoll, a TI-2 antigen) remained statistically above the response of uninfected mice. The response of the resistant strain to either antigen was not modified as a result of the infection. Both strains showed significant polyclonal activation, which was considerably greater in the BALB/c than in the C57BL/6 mice. The observations presented here are in contrast to the widely held belief that a generalized nonspecific immunosuppression occurs in L. tropica infected BALB/c mice.

Idiotype profile of an immune response. II. Reversal of the relative dominance of major and minor cross-reactive idiotypes in arsonate-specific T-independent responses

Two different cross-reactive idiotype (CRI) groups are distinguishable in the Ab response of A/J mice to the p-azobenzenearsonate (ABA) hapten: CRIA and CRIm. These two groups showed distinct patterns of relative dominance in the ensuing response depending on whether the inducing Ag was a T cell-dependent (TD) form of ABA, such as ABA-KLH or ABA-CGG, or a T-independent type 1 (TI-1) form, such as ABA-Brucella abortus or ABA-lipopolysaccharide (LPS), and on whether the response was elicited in vivo or in vitro. The CRI+ component of primary in vivo plaque-forming cell (PFC) responses to TD ABA Ags was largely (greater than 90%) CRIA+ as was, to a slightly lesser extent (greater than 75%) the CRI+ portion of secondary or hyperimmune serum Ab or PFC responses to the same Ags. In contrast, in vivo primary and hyperimmune PFC responses to ABA-Bru or ABA-LPS showed a significantly lower CRIA/CRI ratio, averaging 0.5-0.6, with some individual mice giving figures as low as 0.2, indicating predominance of CRIm over CRIA. Serological analysis of hyperimmune anti-ABA Abs from a group of 5 A/J mice immunized with ABA-Bru gave a figure of less than 0.5 for the CRIA/CRI ratio. The most striking disparity from the TD pattern was seen in primary in vitro PFC responses to the TI ABA Ags; here ratios of less than 0.2 were generally seen. Since T cell removal did not alter the Id pattern in the TI responses, CRIA-specific Ts cells do not account for the weak expression of CRIA in such responses. We propose a model that explains these results on the basis of differential expression of IdX dominance by two distinct B cell subpopulations--equatable to the Lyb-5+ and Lyb-5- B cell subsets--along with differential relative activation of these subsets in different types of responses. Examination of anti-ABA PFC responses of F1 progeny of CBA/N and A/J mice to ABA-Bru lends support to this hypothesis since CRIA expression was significantly lower in mice with the xid defect.

Thymus-independent immunogenicity in vitro of the divalent antigen DNP-polyethylene oxide

Chemically simple and physically well-defined dinitrophenyl derivatives of polyethylene oxide (DNP-PEO) can be prepared in a wide range of forms and sizes. These materials were used to investigate the molecular basis of immunogenicity and the binding of the antigens to membrane-bound receptors. Both di- and multivalent DNP-PEO activate normal murine B lymphocytes to yield primary anti-DNP antibody response in vitro. The immunogenicity is dependent on the carrier chain length but independent of T cells. Responses comparable to those induced by DNP-conjugated polymerized flagellin are induced by divalent linear materials of medium molecular weights of about 60,000. A highly multivalent material is moderately immunogenic, but at much lower antigen doses than divalent materials. The carrier PEO does not affect B-cell responses to DNP-PEO or T-cell response to succinyl concanavalin A. Moreover, it shows no polyclonal mitogenicity at concentrations as high as 1 mg/ml. Studies of antigen binding to cell surface DNP receptors show that the strongly immunogenic materials of medium molecular weights have an appreciable tendency to bind bivalently and thus potentially to crosslink receptors. The binding of smaller, less immunogenic antigen appears predominantly monovalent.

Antibody response of immunodeficient (xid) CBA/N mice to Escherichia coli 0113 lipopolysaccharide, a thymus-independent antigen

CBA/N mice, which possess an X-linked immunodeficiency (xid), produce a convincing antibody response to lipopolysaccharide derived from Escherichia coli 0113 (LPS 0113), a thymus-independent antigen. The antibody response produced was shown to be specific for the O-polysaccharide moiety of LPS 0113, rather than lipid A or lipid-A-associated protein. The relevance of this finding to the nature of the genetic defect of xid-mice is discussed.

Thymus-independent induction and antigen-dependent recovery of idiotype-specific suppression

BALB/c nude (nu/nu) mice and euthymic (nu/+) littermates were treated as neonates with anti-T15 antibody and challenged at various ages with either a thymus-independent, PC-Brucella abortus (PC-BA), or thymus-dependent, PC-keyhole limpet hemocyanin (PC-KLH), form of phosphorylcholine (PC). Nu/nu mice challenged with PC-KLH received KLH-primed splenic T cells prior to immunization. Neither neonatally anti-idiotype-treated nu/+ nor nu/nu mice responded with the production of T15-positive anti-PC antibodies after challenge with either form of PC antigen. It is concluded that neither induction nor maintenance of a state of T15-specific suppression requires thymus-matured T cells. Recovery of anti-PC responsiveness in suppressed nu/+ or nu/nu mice was similar and was found to be related to the form of antigen used to elicit the response. Immunization with PC-KLH revealed a long-lasting unresponsiveness (up to 16 weeks). In contrast, immunization with PC-BA elicited a full anti-PC response as early as at 6.5 weeks of age.

Antibody formation in mouse bone marrow during secondary type responses to various thymus-independent antigens

The data presented in this paper show that different thymus-independent (TI) antigens have a differential capacity of inducing antibody formation in mouse bone marrow, both after primary and secondary intravenous immunization. Primary immunization with certain TI antigens (e.g., lipopolysaccharide [LPS], TNP-LPS, DNP-Ficoll) induces the appearance of antibody-forming cells not only in the spleen, but also in the bone marrow. A single injection of certain other TI antigens (e.g., pneumococci [Pn], TNP-conjugated detoxified LPS [TNP-dLPS], TNP-conjugated Brucella abortus bacteria [TNP-BA] ), on the other hand, induces antibody formation in the spleen only. After secondary immunization with these TI antigens only TNP-BA induces a PFC response in the bone marrow. Pn, TNP-dLPS and TNP-BA, but also DNP-Ficoll, are unable to induce bone marrow antibody formation after secondary injection of the antigen, in spite of the clear-cut secondary type character of the splenic response. Thus, the absence of a bone marrow PFC response after secondary immunization with these antigens is not due to a failure to induce memory B cells. This data implies that either two subpopulations of memory B cells exist, one giving rise to antibody formation in the spleen and the other accounting for the bone marrow response, or that antibody can selectively inhibit the secondary bone marrow antibody response to certain TI antigens.