Thymus independence of a collagen-like synthetic polypeptide and of collagen, and the need for thymus and bone marrow-cell cooperation in the immune response to gelatin

Highly Efficient Excitonic Recombination of Non-polar ([Formula: see text]) GaN Nanocrystals for Visible Light Emitter by Hydride Vapour Phase Epitaxy

While non-polar nanostructured-GaN crystals are considered as a prospective material for the realization of futuristic opto-electronic application, the formation of non-polar GaN nanocrystals (NCs) with highly efficient visible emission characteristics remain unquestionable up to now. Here, we report the oxygen-incorporated a-plane GaN NCs with highly visible illumination excitonic recombination characteristics. Epitaxially aligned a-plane NCs with average diameter of 100 nm were formed on r-plane sapphire substrates by hydride vapor phase epitaxy (HVPE), accompanied by the oxygen supply during the growth. X-ray photoemission spectroscopy measurements proved that the NCs exhibited Ga-O bonding in the materials, suggesting the formation of oxidized states in the bandgap. It was found that the NCs emitted the visible luminescence wavelength of 400‒500 nm and 680‒720 nm, which is attributed to the transition from oxygen-induced localized states. Furthermore, time-resolved photoluminescence studies revealed the significant suppression of the quantum confined Stark effect and highly efficient excitonic recombination within GaN NCs. Therefore, we believe that the HVPE non-polar GaN NCs can guide the simple and efficient way toward the nitride-based next-generation nano-photonic devices.

A Comprehensive Review on Bio-Nanomaterials for Medical Implants and Feasibility Studies on Fabrication of Such Implants by Additive Manufacturing Technique

Nanomaterials have allowed significant breakthroughs in bio-engineering and medical fields. In the present paper a holistic assessment on diverse biocompatible nanocomposites are studied. Their compatibility with advanced fabrication methods such as additive manufacturing for the design of functional medical implants is also critically reviewed. The significance of nanocomposites and processing techniques is also envisaged comprehensively in regard with the needs and futures of implantable medical device industries.

The host response to naturally-derived extracellular matrix biomaterials

Biomaterials based on natural materials including decellularized tissues and tissue-derived hydrogels are becoming more widely used for clinical applications. Because of their native composition and structure, these biomaterials induce a distinct form of the foreign body response that differs from that of non-native biomaterials. Differences include direct interactions with cells via preserved moieties as well as the ability to undergo remodeling. Moreover, these biomaterials could elicit adaptive immune responses due to the presence of modified native molecules. Therefore, these biomaterials present unique challenges in terms of understanding the progression of the foreign body response. This review covers this response to natural materials including natural polymers, decellularized tissues, cell-derived matrix, tissue derived hydrogels, and biohybrid materials. With the expansion of the fields of regenerative medicine and tissue engineering, the current repertoire of biomaterials has also expanded and requires continuous investigation of the responses they elicit.

Antigenicity and immunogenicity of collagen

Pertinent issues of collagen antigenicity and immunogenicity are concisely reviewed as they relate to the design and application of biomedical devices. A brief discussion of the fundamental concepts of collagen immunochemistry is presented, with a subsequent review of documented clinical responses to devices containing reconstituted soluble or solubilized collagen. The significance of atelocollagen, concerns regarding collagen-induced autoimmunity, and other relevant topics are also addressed in the context of current understanding of the human immune response to collagen.

T cell lines generated with type II collagen proliferate in an autologous mixed lymphocyte response

Collagen-induced arthritis (CIA) is a T cell-dependent disease induced in susceptible rodents by immunizing with bovine type II collagen (bCII). In order to study T cell responses, a programme to generate bCII-specific T cell lines from arthritic rats was initiated. Lymph node cells from bCII-immune WA/KIR/kcl rats were cultured with bCII in vitro, and the T cells were isolated and restimulated with bCII-pulsed antigen presenting cells (APC) (thymus cells or splenic low density cells). However, T cells, generated initially to bCII, subsequently proliferated upon co-culture with syngeneic APC even in the absence of bCII. This suggests that exposure to bCII resulted in the activation of a population of self-reactive T cells which proliferate in an autologous mixed lymphocyte response. In contrast, short-term T cell lines generated to ovalbumin, heat-denatured bCII and the collagen peptide bCII(184-198) proliferated in response to specific antigen-pulsed APC without demonstrating self-reactivity. Since denatured bCII and bCII(184-198) peptide are not arthritogenic and failed to generate self reactivity in vitro, this suggests that the native triple helical conformation of bCII is required for stimulating autoreactive T cell responses.

The dominant epitope of Borrelia garinii outer surface protein C recognized by sera from patients with neuroborreliosis has a surface-exposed conserved structural motif

Epitope mapping of outer surface protein C (OspC) by using sera from patients with neuroborreliosis led to the identification of one single major immunodominant epitope within the C-terminal 10 amino acid residues. Peptide binding studies and alanine replacement scanning of the C-terminal decapeptide, PVVAESPKKP, revealed a critical role for the PKKP sequence and its terminal carboxyl group for the binding of immunoglobulin M (IgM) antibodies from patients with Lyme borreliosis. Electron microscopy of antibody-labeled spirochetes indicated that the C-terminal region is exposed on the surface of the spirochete. Based on homology to proteins of known function, this region most probably adopts a polyproline II-like helix, which is found in surface-exposed structures involved in protein-protein interactions. This structural motif is highly conserved in Borrelia species causing Lyme borreliosis and subjected to purifying selection. We suggest that the abundance of the C-terminal region of OspC on the surface of B. burgdorferi allows a multimeric high-avidity interaction between the spirochete and surface Igs on B cells. The resulting cross-linking of surface Igs on B cells may induce a T-cell-independent B-cell activation without IgM-to-IgG switching, thus explaining the lack of IgG antibodies to OspC in neuroborreliosis.

Time course and host responses to Escherichia coli urinary tract infection in genetically distinct mouse strains

Recurrent urinary tract infections (UTIs) are a significant clinical problem for many women; however, host susceptibility factors have not been completely defined. The mouse model of induced UTI provides an experimental environment in which to identify specific host characteristics that are important in initial bacterial colonization of the urinary tract and in resolution of an infection. This study examined initial susceptibility, bacterial clearance, and host defense mechanisms during induction and resolution of Escherichia coli UTIs in genetically distinct strains of mice. Of the ten inbred strains tested, six (BALB/c, C3H/HeN, C57BL/6, DBA.1, DBA.2, and AKR) showed progressive resolution of bladder infections over a 14-day period. A constant, low-level bladder infection was observed in SWR and SJL mice. High bladder infection levels persisted over the 14-day study period in C3H/HeJ and C3H/OuJ mice. Kidney infection levels generally correlated with bladder infection levels, especially in C3H/HeJ and C3H/OuJ mice, the two most susceptible strains, in which infections became more severe with time after challenge. The degree of inflammation in bladder and kidneys, as well as antibody-forming cell responses, positively correlated with infection intensity in all strains except C3H/HeJ, which had minimal inflammation despite high infection levels. These results demonstrate two important aspects of host defense against UTI. First, the innate immune response to an infection in the bladder or kidneys consists primarily of local inflammation, which is followed by an adaptive response characterized in part by an antibody response to the infecting bacteria. Second, a UTI will be spontaneously resolved in most cases; however, in mice with specific genetic backgrounds, a UTI can persist for an extended length of time. The latter result strongly suggests that the presence or absence of specific host genes will determine how effectively an E. coli UTI will be resolved.

Antigenicity of recombinant proteins derived from Plasmodium falciparum merozoite surface protein 1

We have expressed seven recombinant antigens representing two N-terminal regions of the polymorphic merozoite surface protein 1 (MSP-1) of Plasmodium falciparum. The antigens include the MAD20 and Palo Alto forms of the relatively conserved Block 1 region, and variants of the Block 2 region from isolates 3D7, Palo Alto FUP, MAD20, Wellcome and RO33, that are representative of a range or amino acid sequence diversity in this most polymorphic section of MSP-1. All recombinant antigens have been able to immunise mice to produce polyclonal antibodies which specifically recognise parasite MSP-1 in indirect immunofluorescence assays and in Western blots. The recombinant antigens also react appropriately in ELISA with murine monoclonal antibodies specific for variant epitopes in Block 2 of MSP-1. These results show that the antigenic structure of the recombinant proteins is similar to that of the native MSP-1 product from parasites. Importantly, human sera from malaria-exposed individuals contain IgG antibodies that recognise very specifically one or another of the Block 2 types, showing that different Block 2 types are immunogenic, antigenically distinct and distinguishable when presented during natural infections. In contrast, the conserved Block 1 is rarely recognised by human antibodies.

Ia-antigen-T-cell interactions for a thymus-independent antigen composed of D amino acids

Synthetic polypeptide antigens of L amino acids, although bearing repeating sequences, are thymus-dependent (L-TD), whereas the same polymers composed of D amino acids are thymus-independent (D-TI), probably due to a slower rate of metabolism. Yet we found that lymph-node cells of BALB/c mice immunized with D-TI proliferate in response to it in vitro. To follow T-cell activation by D-TI, we established T-cell hybridomas to D-TI and to its analog composed of L isomers, L-TD, for comparison. The T-cell hybridomas express membrane alpha/beta T-cell receptors and secrete interleukin 2 upon stimulation with the respective antigen. In addition, D-TI-specific hybridomas are stimulated, to a lesser extent, by the L-TD antigen, whereas only some L-TD-specific hybridomas recognize D-TI. Moreover, biotinylated analogs of D-TI and L-TD bind to splenic antigen-presenting cells (APCs) from BALB/c mice. Binding is inhibited by an excess of nonbiotinylated L-TD, and by an excess of a peptide comprising residues 259-271 of the human acetylcholine receptor alpha subunit, which binds to I-Ad and I-Ed molecules without prior processing. Analysis of APC lysates following incubation of the APCs with biotinylated D-TI and L-TD reveals that the biotinylated antigen moiety is associated with Ia molecules. D-TI and L-TD bind to Ia molecules on intact APCs with similar KD values, 5 x 10(-8) M and 3 x 10(-8) M, respectively. However, D-TI has faster kinetics of binding than L-TD, probably due to different processing requirements. Hence, we have demonstrated a major histocompatibility complex class II-mediated T-cell response to a thymus-independent antigen.

Tolerogenic activity of polymerized type II collagen in preventing collagen-induced arthritis in rats

Rats were exposed parenterally or pergastrically to polymerized type II collagen (POLCII) and became resistant to the subsequent induction of disease with arthritogenic type II collagen (CII) administered intradermally in Freund's incomplete adjuvant (FIA). POLCII was prepared by cross-linking native soluble arthritogenic CII, from bovine nasal septal cartilage, with glutaraldehyde. POLCII injected intradermally in FIA did not induce arthritis. Animals treated in this manner were resistant for a period of at least 100 days to induced disease. The change in the properties of the CII from an arthritogen to a tolerogen was related to the amount of glutaraldehyde (used to polymerize the CII) which was assumed to control the extent of cross-linking of the CII. Highly cross-linked POLCII administered pergastrically, like soluble CII, was not arthritogenic but was tolerogenic, inducing a state of unresponsiveness to a challenge with arthritogenic CII. In general serum anti-CII antibody levels were higher in arthritic than in tolerized non-arthritic rats. It is concluded that the breaking of self-tolerance to CII depends upon its physical state. When polymerized and insoluble, a form analogous to that in which it exists naturally, it is tolerogenic.

The anti-arthritic and immunosuppressive effects of cyclosporine on arthritis induced in the rat by type II collagen

The influence of cyclosporine (CsA) on the induction and pathogenesis of type II collagen-induced arthritis has been investigated in inbred and outbred Wistar rats. The proportion of animals developing disease and the severity of disease they developed were both diminished by treatment with CsA. These effects were accompanied by a marked suppression of the antibody response to both the immunizing collagen and also to rat type II collagen. CsA treatment also resulted in a decreased accumulation of lymphocytes in arthritic joints. The results indicate that the anti-arthritic and immunosuppressive effects of CsA probably result from a modification of both systemic antibody-mediated and local cell-mediated immunity.

Role of T lymphocytes in collagen II induced arthritis in rats

The role of T lymphocytes in collagen II induced arthritis in rats has been investigated. Functional T cells were needed for the development of arthritis since none out of 14 nude rats injected with collagen type II developed arthritis, whereas 11 out of 14 of their normal counterparts did. With the help of antibodies specific for Ia antigens and different T cell subsets in the rats, an immunohistochemical method was used to demonstrate that T cells, predominantly of `helper' type and anti-Ia reactive non-T cells were abundant in the arthritic synovial tissue.

Requirement for T cells in the antibody response of mice to calf skin collagen

The antibody response to triple-helical calf skin collagen is apparently regulated by T cells since nude mice (BALB/c strain) responded to this antigen only after transfer of T cells. Syngeneic transfer of B and T cells was required to prepare thymectomized and irradiated normal C57B1/10 recipients for an anti-collagen response. Reconstitution by B cells alone was unsuccessful. The results are compatible with previous evidence on the H-2 linked genetic control of the antibody response to and the non-repetitious nature of helical antigenic determinants in calf collagen.

The effect of the thymus-independent antigens, collagen and synthetic collagen-like polypeptide, on the requirement of cell cooperation in the immune response to thymus-dependent antigens

The effect of thymus-independent antigens on the need for cell cooperation in the immune response to thymus-dependent antigens was investigated. Irradiated recipient mice transplanted with either bone marrow cells or a mixture of bone marrow and thymus cells, were immunized with the thymus-independent antigen (Pro-Gly-Pro)n covalently conjugated to the thymus-dependent ovalbumin, or with a mixture of (Pro-Gly-Pro)n and ovalbumin. In both cases an effective response towards ovalbumin was observed in the absence of thymus cells as was found for the thymus-independent (Pro-Gly-Pro)n. The same effect on ovalbumin was demonstrated when a mixture of the thymus-independent collagen and ovalbumin was used for immunization. On the other hand, when irradiated reconstituted mice were immunized with a mixture of ovalbumin and the thymus-dependent gelatin, which is the denatured product of collagen, cell-to-cell cooperation was required for an immune response to both immunogens. The effect of (Pro-Gly-Pro)n and collagen on the response to the thymus-dependent ovalbumin in vivo was observed in in vitro experiments using sheep red blood cells (SRBC) as the immunogen as well. In the presence of reduced and carboxymethylated (RCM) Ascaris collagen and (Pro-Gly-Pro)n, nude spleen cells could produce significant numbers of plaque-forming cells towards SRBC. Thus, (Pro-Gly-Pro)n and collagen can deliver the signal required to stimulate B cells to produce antibody towards thymus-dependent antigens in the absence of T cells. In contrast to the results with (Pro-Gly-Pro)n and collagen, the thymus-independent synthetic polypeptide poly(DTyr, DGlu-)-poly(DPro)--poly(DLys) did not affect the requirement for cell cooperation of the thymus-dependent immunogens, ovalbumin and SRCB. It thus appears that the ability to substitute for T cells for antibody production towards thymus-dependent immunogens is not a general characteristic of thymus-independent antigens.

Separation of antigen-specific lymphocytes. II. Enrichment of hapten-specific antibody-forming cell precursors

Normal spleen cells were separated in dishes coated with thin layers of DNP-gelatin or NIP-gelatin into binding and nonbinding cells and stimulated in vitro with DNP- and/or NIP-conjugated polymerized flagellin (POL). Hapten-specific unresponsiveness was induced in the binding cell population by melting the gel at 37 degrees C or in unfractionated cells by pretreatment with soluble hapten-gelatin and could be reversed by treatment with collagenase. A specific enrichment of anti-DNP and anti-NIP antibody-forming cell precursors (AFCP) could be demonstrated in the binding cell populations after treatment with collagenase in cultures with or without "feeder" cells. However, the response of small numbers of unfractionated and purified hapten-specific spleen cells was suboptimal even in the presence of mitomycin-treated or irradiated feeder cells. Optimal numbers of anti-DNP (anti-NIP) antibody-forming cells were generated by small numbers of normal or purified spleen cells in the presence of spleen cells depleted of anti-DNP (anti-NIP) AFCP. In this system the response of only 2 times 10-4 purified hapten-specific cells was higher than the response of 10-6 unfractionated cells. Purified DNP-specific cells responded only to DNP-POL but not to NIP-POL and purified NIP-specific cells responded only to NIP-POL but not to DNP-POL. The degree of enrichment of anti-DNP AFCP decreased with increasing numbers of binding cells. NIP3-gelatin layers bound four to five times less spleen cells than DNP2-gelatin layers and the enrichment of anti-NIP AFCP (about 300-fold) was three times greater than the enrichment of anti-DNP AFCP (about 100-fold). The immunological significance of hapten-gelatin binding cells which apparently failed to respond to antigen is discussed.

H-2-linked genetic control of antibody response to soluble calf skin collagen in mice

An autosomal dominant immune response gene could be demonstrated in congenic resistant strains of mice which is linked to the H-2 locus and controls the antibody response to soluble calf collagen. High responsiveness was associated with the H-2 alleles, b and f, low responsiveness with the H-2 alleles, d, k, m and r. Studies with calf procollagen, which contains an additional carrier moiety, indicated that these genetic differences might be expressed at the level of T cells.

Lack of requirement for thymocytes for efficient antibody formation to trinitrophenylated mouse red cells in mice: role for thymocytes in suppression of the immune response

The requirement of thymus-derived cells for the immune response to trinitrophenylated syngeneic mouse red cells (TNP-MRC) was investigated. In three sets of experiments the following results were obtained: a) irradiated mice which were reconstituted with bone marrow cells alone showed a better anti-TNP response after injection with TNP-MRC than those reconstituted with both bone marrow cells and thymocytes. b) Anti-thymocyte serum augmented the mouse anti-TNP response to TNP-MRC. c) Nude thymusless mice showed a better anti-TNP response to TNP-MRC than their normal littermate controls. These results indicate that the anti-TNP response of mice to TNP-MRC does not require thymus-derived helper cells. Moreover, thymus-derived cells have a suppressive effect on the anti-TNP response.

The immunological properties of haptens coupled to thymus-independent carrier molecules. III. The role of the immunogenicity and mitogenicity of the carrier in the induction of primary IgM anti-hapten responses

Hapten (DNP-lys) conjugates of two putatively nonimmunogenic polymers, hyalutonic acid and poly-gamma-D-glutamic acid, induce significant primary IgM anti-DNP responses in C3H mice. Preparations of various immunogenic (Type 3 pneumococcal polysaccharide (SIII), levan, E. coli lipopolysaccharide) and nonimmunogenic (hyaluronic acid and poly-glutamic acid) polymers were tested for their ability to act as polyclonal mitogens in vitro. In serum-containing spleen cell cultures, only lipopolysaccharide stimulated substantial cell proliferation. In serum-free medium, and using high specific activity [3H]thymidine, lipopolysaccharide, levan, SIII and to a lesser degree hyaluronic acid induced significant thymidine incorporation. However, under the latter conditions cell survival and proliferation were much less impressive. There was no apparent correlation between the capacity of various polymers to induce lymphocyte proliferation and their "potency" as carriers for the generation of a primary IgM anti-DNP response. Furthermore while low doses of lipopolysaccharide elicited "polyclonal" antibody formation in vivo, high doses of SIII, levan and hyaluronic acid did not. These results indicate that T cell-independent B cell triggering is dependent on the polymeric nature of the antigen, and that polymers need not be immunogenic or mitogenic to act as carriers for the induction of primary IgM anti-hapten antibody responses.