Thymus-dependent Antigen Research Articles

Changes in some parameters of immune response under the effect of adrenoceptor blockers

We studied the effect of α-and β-adrenoceptor blockers on humoral and cell immune response in (CBA×C57Bl/6)F1 mice under normal conditions and during stress. The suppressive effect of α-adrenoceptor blocker dihydroergotamine on humoral immune response against the background of both immunization and combined effects of immobilization and injection of a thymus-dependent antigen was more pronounced compared to that of β-adrenoceptor blocker propranolol. Dihydroergotamine suppressed proliferative activity of T cells, stimulated proliferation of B cells at late terms after immunization, but inhibited it against the background of stress and antigen treatment. Propranolol stimulated proliferative activity of T and B cells at early terms after both immunization alone and stress with antigen treatment, but decreased the proliferation stimulation index of lymphoid cells at late terms after treatment (days 7–10).

The germinal center response is impaired in the absence of T cell‐expressed CXCR5

Germinal centers support the differentiation of memory B cells and long-lived antibody-secreting cells during infection or upon vaccination. Here, we constructed mice with T cells that selectively lack the chemokine receptor CXCR5 to determine if expression of this receptor by T cells is mandatory for germinal center formation and function. In these animals, germinal centers that are properly localized in B cell follicles and contain T cells do form after immunization with a thymus-dependent antigen. However, fewer and smaller germinal centers form, resulting in a significant reduction in the frequency of germinal center B cells. The defect in germinal center formation is paralleled by decreased frequencies of isotype-switched antibody-secreting cells in the spleen and bone marrow and reduced serum concentrations of total and high-affinity hapten-specific IgG1. The results demonstrate that although CXCR5-dependent T cell positioning is important for maximal induction and expansion of germinal centers, stimulation of isotype class switching, and development of antibody-secreting cells that seed the spleen and bone marrow, it is not absolutely required for the formation and function of follicular germinal centers.

Kinase MEKK1 is required for CD40-dependent activation of the kinases Jnk and p38, germinal center formation, B cell proliferation and antibody production

Mice lacking activity of the kinase MEKK1 ('Map3k1(deltaKD)' mice) have defective activation of the kinase Jnk and increased production of T helper type 2 cytokines after T cell receptor ligation. Here we show that Map3k1(deltaKD) mice had defective germinal center formation and diminished production of antibodies recognizing thymus-dependent antigens. Those defects were B cell intrinsic, as MEKK1 was necessary for CD40-mediated activation of the kinases Jnk and p38 and transcription factor c-Jun, as well as for expression of cyclin D2 and activation-induced deaminase. MEKK1 was recruited to CD40 and adaptor molecule TRAF2 after CD40 ligation, and Map3k1(deltaKD) B cells were hypoproliferative after CD40 stimulation. Our data emphasize that MEKK1 is an essential component of signaling cascades needed for thymus-dependent antigen-induced B cell proliferation and antibody production.

A Novel Role for Caveolin-1 in B Lymphocyte Function and the Development of Thymus-Independent Immune Responses

Caveolin-1 (Cav-1) functions as a scaffold or platform for many molecules involved in signal transduction. However, the expression and function of Cav-1 in the immune system has been controversial. Here, we show that Cav-1 mRNA and protein is indeed expressed in murine B-lymphocytes in a regulated manner. Cav-1 deficient mice displayed reduced levels of antibody in their serum. In order to examine the role of Cav-1 in the development of immunoglobulin-mediated immune responses, we immunized wild-type and Cav-1 deficient mice with thymus-dependent and thymus independent antigens. Our results show that Cav-1 deficient mice have a normal response to thymus-dependent antigens, but have a reduced response to both type I and type II thymus independent antigens. However, lymphocyte populations in the spleen and peritoneum were not altered and no changes were observed in splenic architecture. Caveolin-1 deficient B-lymphocytes did not display altered proliferation in response to different stimuli. However, we found that Cav-1 deficient B cells have reduced IgG3 secretion in vitro in response to LPS. Finally, we also demonstrate that human plasma cells (mature B lymphocytes) express Cav-1 in vivo. Taken, together these results provide convincing evidence for expression of Cav-1 in activated B-lymphocytes and demonstrate a role for Cav-1 in the development of thymus-independent immune responses.

BOB.1/OBF.1 - A Critical Regulator of B Cell Function

The transcriptional coactivator BOB.1/OBF.1 binds as a ternary complex with the transcription factors Oct-1 and Oct-2 to DNA and induces octamer-dependent transcription. BOB.1/OBF.1 was shown to be necessary at multiple stages of B cell development, in the bone marrow as well as at late stages in secondary lymphoid organs. Bone marrow B cells from BOB.1/OBF.1-deficient mice show increased apoptosis accompanied with decreased expression levels of the anti-apoptotic protein Bcl2. Although transgenic B cell-specific expression of Bcl2 rescued the numbers and maturation of BOB.1/OBF.1-deficient B cells in the bone marrow as well as in peripheral lymphoid organs, the B cell function was still severely impaired. The most prominent characteristic of BOB.1/OBF.1 knock-out mice is the complete failure to form germinal centers upon immunization with thymic-dependent antigens and consequently a massive defect in production of secondary Ig isotypes. In addition, the marginal zone B cell compartment, first line defence against blood born antigens, is virtually absent in BOB.1/OBF.1 -/- animals. A large number of genes specifically expressed in B cells contain octamer motifs in their regulatory regions, but only a small number of BOB.1/OBF.1 dependent genes are described yet. To understand the molecular basis of BOB.1/OBF.1 function in B cell development we and others searched for BOB.1/OBF.1 target genes. A large number of BOB.1/OBF.1-dependent genes were identified, which are involved in different aspects of lymphocyte development and signaling, supporting the critical regulatory role of BOB.1/OBF.1 for lymphocyte function. Here we summarize recent developments highlighting the central role that BOB.1/OBF.1 plays in B lymphocytes. Keywords: BOB.1/OBF.1, OCA-B, germinal center, target genes, B cell development, B cell function, octamer motif

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.

Mature B Cells: Apoptosis Checkpoints

In the present review, the apoptosis mechanisms that ensure efficiency of the B cell responses and homeostasis of mature B cells are examined. The general scheme that emerges from the literature is that these two phenomena are under the control of distinct apoptotic pathways. The extrinsic death receptor pathway intervenes in the quality control of the B cell response to thymus-dependent antigens. It prevents the bystander activation of irrelevant B cell clones and is instrumental in the affinity maturation of the antibody response. The intrinsic death pathway is responsible for homeostasis of the naive, effector, and memory B cell compartments. Recent results suggest the stress signal that triggers this pathway may be initiated by different cellular organelles depending on the B cell developmental stage.

B Cells and Alloantibodies in Tolerance: A New Look

B Cells and Alloantibodies in Tolerance: A New Look

Effect of Honey on Antibody Production Against Thymus-Dependent and Thymus-Independent Antigens in Primary and Secondary Immune Responses

The objective was to study the effect of natural pure honey on the antibody production against thymus-dependent antigen [sheep red blood cells (SRBCs)] and thymus-independent antigen (Escherichia coli) in mice. Forty-two mice (mean weight 28.33 +/- 3.44 g) were divided into two groups: group A (21 mice) fed regular diet and group B (21 mice) fed regular diet plus 0.8 g/kg of body weight/day of honey administered in four equally divided doses. Each animal was injected intraperitoneally with 0.1 mL of 5% SRBCs and 0.1 mL of killed E. coli. The same dose of both antigens was given after 17 days. At days 7 and 16 after primary immunization and at day 4 after secondary immunization, blood samples were collected from seven mice at each time interval from group A and group B to estimate antibody titer using the hemoaggulination test. At day 7 after primary immunization, the mean antibody titer against SRBCs was 9.14 +/- 3.02 in group A and 13.7 +/- 3.9 in group B (P < .05), while the mean antibody titer against E. coli was 14.8 +/- 8.5 in group A and 14.8 +/- 9.35 in group B. At day 16, the mean antibody titer against SRBCs was 13.71 +/- 3.9 in group A and 20 +/- 9.8 in group B, while the mean antibody titer against E. coli was 14.69 +/- 935 in group A and 26.67 +/- 8.26 in group B (P < .05). Four days after secondary immunization, the mean antibody titer against SRBCs was 13.33 +/- 4.62 in group A and 16 +/- 8.7 in group B, while the mean antibody titer against E. coli was 42.67 +/- 18.4 in group A and 69.33 +/- 31.4 in group B. It might be concluded that oral honey stimulates antibody production during primary and secondary immune responses against thymus-dependent and thymus-independent antigens.

Comparative Analysis of Signal Transduction by CD40 and the Epstein-Barr Virus Oncoprotein LMP1 In Vivo

There is much evidence, based primarily on in vitro studies, indicating that the Epstein-Barr virus oncoprotein latent membrane protein 1 (LMP1) mimics an activated CD40 receptor. In order to investigate the extent of similarity between LMP1 and CD40 functions in vivo, we analyzed the cytoplasmic signaling properties of LMP1 and CD40 in B cells in a directly comparable manner. For this purpose, we generated transgenic mice expressing either LMP1 or a chimeric LMP1CD40 molecule, which constitutively activates the CD40 pathway, under the control of the CD19 promoter. LMP1 and LMP1CD40 were expressed at similar levels in a B-lymphocyte-specific manner. Similar to LMP1, LMP1CD40 suppressed germinal center (GC) formation and antibody production in response to thymus-dependent antigens, albeit to a greater extent than LMP1. Furthermore, the avidity of the antibodies produced against thymus-dependent antigens was lower for LMP1CD40 transgenic mice than for wild-type and LMP1 transgenic mice. GC suppression was linked to the ability of LMP1CD40 and LMP1 to downregulate mRNA and protein levels of BCL6 and to suppress the activity of the BCL6 promoter. In contrast to LMP1, LMP1CD40 caused an upregulation of CD69, CD80, and CD86 in B cells and a dramatic increase in serum immunoglobulin M. In addition, LMP1CD40 but not LMP1 transgenic mice had elevated numbers of marginal-zone B cells and increased populations of polymorphonuclear cells and/or neutrophils. Consistent with these findings, LMP1CD40 but not LMP1 transgenic mice showed signs of spontaneous inflammatory reactions and the potential for autoimmunity.

The Immune Response in Mice with Psychoemotional Stress under the Conditions of a Decreased Serotonin Synthesis in the Brain

formity with the Regulations of the Committee for Biomedical Ethics ), which is a strong psychoemotional impact for rodents [9]. The model of paired sensory contact [4] was used for 10 days to develop submissive behavior. Submissive animals were identified on the basis of specific behavioral elements: the postures of vertical and side defense against an attacker, fleeing, immobile postures of complete submission (“freezing” and “supine”). After the stress and after 10 days of the formation of submissive behavior, mice were immunized into a tail vein with the thymus-dependent antigen sheep red blood cells (SRBCs) at a dose of 5 × 10 8 cells. The immune response was evaluated on the

Andrographolide Interferes with T Cell Activation and Reduces Experimental Autoimmune Encephalomyelitis in the Mouse

Andrographolide is a bicyclic diterpenoid lactone derived from extracts of Andrographis paniculata, a plant indigenous to South Asian countries that shows anti-inflammatory properties. The molecular and cellular bases for this immunomodulatory capacity remain unknown. Here, we show that andrographolide is able to down-modulate both humoral and cellular adaptive immune responses. In vitro, this molecule was able to interfere with T cell proliferation and cytokine release in response to allogenic stimulation. These results were consistent with the observation that T cell activation by dendritic cells (DCs) was completely abolished by exposing DCs to andrographolide during antigen pulse. This molecule was able to interfere with maturation of DCs and with their ability to present antigens to T cells. Furthermore, in vivo immune responses such as antibody response to a thymus-dependent antigen and delayed-type hypersensitivity were drastically diminished in mice by andrographolide treatment. Finally, the ability of andrographolide to inhibit T cell activation was applied to interfere with the onset of experimental autoimmune encephalomyelitis (EAE), an inflammatory demyelinating disease of the central nervous system that is primarily mediated by CD4(+) T cells and serves as an animal model for human multiple sclerosis. Treatment with andrographolide was able to significantly reduce EAE symptoms in mice by inhibiting T cell and antibody responses directed to myelin antigens. Our data suggest that andrographolide is able to efficiently block T cell activation in vitro, as well as in vivo, a feature that could be useful for interfering with detrimental T cell responses.

5. IgE, mast cells, basophils, and eosinophils

IgE, mast cells, basophils, and eosinophils constitute essential elements in allergic inflammation. Allergen-specific IgE, synthesized in response to allergens in the environment, becomes fixed to FcepsilonRI on the membranes of mast cells and basophils. Aggregation of receptor-bound IgE molecules on re-exposure to specific allergen results in the production of mediators that produce the allergic response. Principal among the cells drawn to sites of mediator release is the eosinophil.

Antimetastatic effect of thymus-dependent antigen (sheep erythrocytes) in C57BL/6 mice with Lewis carcinoma.

We revealed an antimetastatic effect of thymus-dependent corpuscular antigen (sheep erythrocytes) injected intravenously or intraperitoneally in sensitizing or high doses alone or in a complex with a course dose of cyclophosphamide to C57Bl/6 mice with Lewis carcinoma. Injection of the antigen appreciably reduced the number and volume of Lewis carcinoma metastases in the lungs, notably increased the therapeutic effect of cyclophosphamide, and restored hemopoiesis, particularly, the red blood stem suppressed by the tumor process and cytostatic treatment. The growth of primary tumors virtually did not change. High dose of sheep erythrocytes was more effective.

Immunological function in mice lacking the Rac-related GTPase RhoG.

RhoG is a low-molecular-weight GTPase highly expressed in lymphocytes that activates gene transcription and promotes cytoskeletal reorganization in vitro. To study the in vivo function of RhoG, we generated mice homozygous for a targeted disruption of the RhoG gene. Despite the absence of RhoG, the development of B and T lymphocytes was unaffected. However, there was an increase in the level of serum immunoglobulin G1 (IgG1) and IgG2b as well as a mild increase of the humoral immune response to thymus-dependent antigens. In addition, B- and T-cell proliferation in response to antigen receptor cross-linking was slightly increased. Although RhoG deficiency produces a mild phenotype, our experiments suggest that RhoG may contribute to the negative regulation of immune responses. The lack of a strong phenotype could indicate a functional redundancy of RhoG with other Rac proteins in lymphocytes.

Reactions of immune system to immobilization stress in inbred mice of different strains.

Mice of different strains can be classified by the intensity of humoral immune reaction to thymus-dependent antigen as high, moderate, and low responders. High and moderate responders (CBA/CaLac, DBA/1, BALB/c) are characterized by high sensitivity of the productive phase of humoral immune response and phagocytic activity of macrophages to immobilization stress. In low responders (C57BL/6, CC57W) stress only slightly affected the productive phase of the humoral immune response, but activity of peritoneal macrophages decreased. These differences in the reactions of the immune system of inbred mice after immobilization stress reflect different reactions of the immune system to extreme factors.

Non-genetic inheritable potential of maternal antibodies

Maternal antibodies (IgG and IgA) not only provide passive protection against microbial infections, but also exert a variety of equally important active, idiotypically-mediated immunoregulatory functions. Since the generation of maternal antibodies depends entirely on the stimulation of the mother’s immune system by external mainly thymus-dependent antigens, with long-lived antigen independent plasma cells in the bone marrow, maternal antibodies represent the mother’s collective ontogenetic immunological experience. Although their stimulatory potential in mice is restricted to the neonatal imprinting period, maternal antibodies exert a life-long determinative influence which is even dominant over seemingly genetic predispositions. Therefore, the functional impact of maternal IgG antibodies appears phenotypically as a non-genetic inheritance.

Ultralow doses of anti-idiotypic antibodies to human gamma-interferon: immunotropic properties.

We studied the effects of ultralow doses of anti-idiotypic antibodies to human gamma-interferon on humoral immune response in experimental animals immunized with a thymus-dependent antigen, delayed-type hypersensitivity, and phagocytic activity of neutrophils in the peritoneal exudate. This preparation stimulated the humoral immune response and activated phagocytosis, but had no effect on functional activity of T cells.

A crucial role for the p110delta subunit of phosphatidylinositol 3-kinase in B cell development and activation.

Mice lacking the p110δ catalytic subunit of phosphatidylinositol 3-kinase have reduced numbers of B1 and marginal zone B cells, reduced levels of serum immunoglobulins, respond poorly to immunization with type II thymus-independent antigen, and are defective in their primary and secondary responses to thymus-dependent antigen. p110δ−/− B cells proliferate poorly in response to B cell receptor (BCR) or CD40 signals in vitro, fail to activate protein kinase B, and are prone to apoptosis. p110δ function is required for BCR-mediated calcium flux, activation of phosphlipaseCγ2, and Bruton's tyrosine kinase. Thus, p110δ plays a critical role in B cell homeostasis and function.

The humoral response in TCR alpha-/- mice. Can gammadelta-T cells support the humoral immune response?

An optimal humoral response requires T-cell help; however, it has been questioned if this help comes exclusively from alphabeta-T cells or whether gammadelta-T cells also contribute. We have attempted to answer this question by studying the humoral response in T-cell receptor alpha-chain knockout (alpha-/-) mice, which lack the alphabetaT cell subset. Two model antigens were used to characterize the response: the thymus-independent (TI) antigen native dextran B512 (Dx), and the thymus-dependent (TD) antigen heat shock protein (HSP65) from Mycobacterium tuberculosis. When challenged with Dx, the alpha-/- mice elicited a strong antibody response and formed rudimentary germinal centres (GCs), a T-cell dependent reaction. In contrast, the humoral response to HSP65 was poor. However, alpha-/- mice became primed when challenged with HSP65, because when supplemented with wild-type thymocytes, the antigen-primed animals were able to mount a stronger response than the nonprimed ones when challenged with HSP65. A crucial step seems to be the collaboration between gammadeltaT cells and antigen presenting cells (APCs), as splenocytes from alpha-/- mice were able to respond to HSP65 in an environment containing primed-APCs. Based on these results, we propose a model for B-cell activation in the alpha-/- mice.