THE HETEROGENEITY OF THE IMMUNE RESPONSE

The neuroimmune axis of Alzheimer's disease

Alzheimer's disease (AD) is a genetically complex and heterogeneous disorder with multifaceted neuropathological features, including β-amyloid plaques, neurofibrillary tangles, and neuroinflammation. Over the past decade, emerging evidence has implicated both beneficial and pathological roles for innate immune genes and immune cells, including peripheral immune cells such as T cells, which can infiltrate the brain and either ameliorate or exacerbate AD neuropathogenesis. These findings support a neuroimmune axis of AD, in which the interplay of adaptive and innate immune systems inside and outside the brain critically impacts the etiology and pathogenesis of AD. In this review, we discuss the complexities of AD neuropathology at the levels of genetics and cellular physiology, highlighting immune signaling pathways and genes associated with AD risk and interactions among both innate and adaptive immune cells in the AD brain. We emphasize the role of peripheral immune cells in AD and the mechanisms by which immune cells, such as T cells and monocytes, influence AD neuropathology, including microglial clearance of amyloid-β peptide, the key component of β-amyloid plaque cores, pro-inflammatory and cytotoxic activity of microglia, astrogliosis, and their interactions with the brain vasculature. Finally, we review the challenges and outlook for establishing immune-based therapies for treating and preventing AD.

Dominant IgM synthesis against the soluble form of the prevailing variant surface glycoprotein from TeAp-N/D1 Trypanosoma equiperdum throughout the experimental acute infections of horses with non-tsetse transmitted Trypanozoon parasites

Two horses were infected with distinct non-tsetse transmitted Trypanozoon Venezuelan stocks, namely TeAp-N/D1 Trypanosoma equiperdum and TeAp-El Frio01 Trypanosoma evansi. Preceding reports have revealed that a 64-kDa antigenic glycopolypeptide (p64), which is the soluble form of the predominant variant surface glycoprotein from TeAp-N/D1 T. equiperdum, can be used as a good antigen for immunodiagnosis of animal trypanosomosis. Here, the course of the experimental acute infection in both horses was monitored by evaluating total anti-p64 IgG and particular anti-p64 γ-specific IgG and μ-specific IgM isotypes in sera using indirect enzyme-linked immunosorbent assays. Both equines showed a maximum of whole anti-p64 antibody generation, which dropped to readings below the maximum but always above the positive cutoff point. Levels of specific IgG and IgM isotypes oscillated throughout the course of the experiments. Essentially, the γ-specific IgG response remained very close to the cutoff point, whereas the μ-specific IgM response displayed values that were mostly above the positive cutoff point, showing a major peak that coincided with the maximum of complete anti-p64 IgG production. These results showed that horses infected with non-tsetse transmitted Trypanozoon parasites developed an immune reaction characterized by a dominant IgM generation against the p64 antigen.

An Integrated Plasmo-Photoelectronic Nanostructure Biosensor Detects an Infection Biomarker Accompanying Cell Death in Neutrophils

Bacterial infections leading to sepsis are a major cause of deaths in the intensive care unit. Unfortunately, no effective methods are available to capture the early onset of infectious sepsis near the patient with both speed and sensitivity required for timely clinical treatment. To fill the gap, the authors develop a highly miniaturized (2.5 × 2.5 µm² ) plasmo-photoelectronic nanostructure device that detected citrullinated histone H3 (CitH3), a biomarker released to the blood circulatory system by neutrophils. Rapidly detecting CitH3 with high sensitivity has the great potential to prevent infections from developing life-threatening septic shock. To this end, the author's device incorporates structurally engineered arrayed hemispherical gold nanoparticles that are functionalized with high-affinity antibodies. A nanoplasmonic resonance shift induces a photoconduction increase in a few-layer molybdenum disulfide (MoS₂ ) channel, and it provides the sensor signal. The device achieves label-free detection of serum CitH3 with a 5-log dynamic range from 10^-4 to 10¹ ng mL and a sample-to-answer time <20 min. Using this biosensor, the authors longitudinally measure the dynamic CitH3 profiles of individual living mice in a sepsis model at high resolution over 12 hours. The developed biosensor may be poised for future translation to personalized management of systemic bacterial infections.

Immunological memory: What's in a name?

Immunological memory is one of the core topics of contemporary immunology. Yet there are many discussions about what this concept precisely means, which components of the immune system display it, and in which phyla it exists. Recent years have seen the multiplication of claims that immunological memory can be found in "innate" immune cells and in many phyla beyond vertebrates (including invertebrates, plants, but also bacteria and archaea), as well as the multiplication of concepts to account for these phenomena, such as "innate immune memory" or "trained immunity". The aim of this critical review is to analyze these recent claims and concepts, and to distinguish ideas that have often been misleadingly associated, such as memory, adaptive immunity, and specificity. We argue that immunological memory is a gradual and multidimensional phenomenon, irreducible to any simple dichotomy, and we show why adopting this new view matters from an experimental and therapeutic point of view.

The Memory Function of the B Cell Antigen Receptor

Activated B lymphocytes preserve their antigen experience by differentiating into long-lived pools of antibody-secreting plasma cells or various types of memory B cells (MBCs). The former population constantly produces serum immunoglobulins with sufficient specificity and affinity to thwart infections with recurrent pathogens. By contrast, memory B cell populations retain their antigen receptors on the cell surface and hence need pathogen-induced differentiation steps before they can actively contribute to host defense. The terminal differentiation of MBCs into antibody-secreting plasma cells is hallmarked by the absence of the lag phase characteristic for primary antibody responses. Moreover, secondary antibody responses are predominantly driven by MBCs that bear an antigen receptor of the IgG class on their surface although IgM-positive memory populations exist as well. These fundamental principles of B cell memory were enigmatic for decades. Only recently, we have begun to understand the underlying mechanisms. This review summarizes our current understanding of how different subpopulations of MBCs are generated during primary immune responses and how their functional heterogeneity on antigen recall is controlled by different signaling capabilities of B cell antigen receptor (BCR) isotypes and by the nature of the antigen.

The immunoglobulin tail tyrosine motif upgrades memory-type BCRs by incorporating a Grb2-Btk signalling module

The vigorous response of IgG-switched memory B cells to recurring pathogens involves enhanced signalling from their B-cell antigen receptors (BCRs). However, the molecular signal amplification mechanisms of memory-type BCRs remained unclear. Here, we identify the immunoglobulin tail tyrosine (ITT) motif in the cytoplasmic segments of membrane-bound IgGs (mIgGs) as the principle signal amplification device of memory-type BCRs in higher vertebrates and decipher its signalling microanatomy. We show that different families of protein tyrosine kinases act upstream and downstream of the ITT. Spleen tyrosine kinase (Syk) activity is required for ITT phosphorylation followed by recruitment of the adaptor protein Grb2 into the mIgG-BCR signalosome. Grb2 in turn recruits Bruton's tyrosine kinase (Btk) to amplify BCR-induced Ca(2+) mobilization. This molecular interplay of kinases and adaptors increases the antigen sensitivity of memory-type BCRs, which provides a cell-intrinsic trigger mechanism for the rapid reactivation of IgG-switched memory B cells on antigen recall.

EFFECT OF 6-MERCAPTOPURINE (6-MP) ON DIFFERENT CLASSES OF ANTIBODY

In the primary response of mice and rabbits immunized with foreign red cells, 6-MP administration prolonged the formation of 19S antibody. 7S antibody formation was delayed and reduced in these animals. Animals treated with 6-MP during primary response exhibited a preferential 19S response when challenged in the anamnestic response. Animals immunized with small doses of antigen and treated with 6-MP only during the secondary response, reversed the usual antibody pattern and responded with preferential 19S antibody formation.

CELLULAR SITES OF SYNTHESIS OF RABBIT IMMUNOGLOBULINS DURING PRIMARY RESPONSE TO DIPTHERIA TOXOID-FREUND'S ADJUVANT

The present studies are based on previous observations that the intravenous injection of diphtheria toxoid and complete Freund's adjuvant into rabbits resulted in an increased proliferation of cells associated with antibody synthesis; an accelerated, enhanced, and prolonged synthesis of antibody; and a lengthened interval between the appearance of γM- and γG-hemagglutinating antibodies in the circulation. The molecular species of antibodies that were synthesized by fragments of the spleens were determined by the incorporation of labeled amino acid into antibody and by binding of radioactive antigen by antibody. These studies were paralleled by determination of the presence and type of antibody within the cell by immunofluorescence. Evidence was obtained that non-phagocytic mononuclear cells in the walls of the sinusoids of the red pulp of the spleen are a major source of 19S γM-antibody and plasma cells in the non-follicular white pulp are a major source of γG-antibody. The data did not exclude the synthesis of γG-antibodies by the mononuclear cells, the synthesis of γM-antibodies by the plasma cells, or the synthesis of both antibodies by an occasional cell of either morphology. It was hypothesized that the 19S and 7S antibody responses evolved independently with the development of at least two different cell types, a mononuclear cell with capacity for 19S immunoglobulin synthesis and a plasma cell with capacity for 7S immunoglobulin synthesis.

THE ENHANCEMENT OF 19S ANTIBODY PRODUCTION BY PARTICULATE ANTIGEN

Injection of human thyroglobulin solution into rabbits gave rise to a transient 19S antibody response which could however be maintained by repeated administration of antigen. When the antigen was coated onto acrylic resin particles, the titre of 19S antibodies was increased nearly 20-fold whereas 7S antibody levels were unchanged. This selective enhancement of 19S antibody synthesis by particulate antigen was also seen using human γ-globulin. "Intermediate" sedimenting and 7S γ₁-antibodies were also increased in animals given particulate antigen. These phenomena may be due to prolonged persistence of the antigen in appropriate macrophages or perhaps to an increased uptake into these cells. The results are discussed in terms of the relationship between 19S and 7S globulin-producing cells.

ABNORMAL IMMUNE MECHANISM IN ALLOGENEIC RADIATION CHIMERAS

Mice were subjected to x-rays (950 roentgens) and injected with isogeneic (isologous) or allogeneic (homnologous) bone marrow. Six to 8 months later these chimeras were injected with Salmonella typhi flagellar antigen, and the formation of antibodies resistant and sensitive to destruction by treatment in vitro with 2-mercaptoethanol was determined. The allogeneic chimeras showed almost normal amounts of serumn antibody after a third injection of antigen but a relative defect in their ability to synthesize antibody resistant to 2-mercaptoethanol. Apparently control of antibody formation becomes abnormal in the presence of the immunologic tolerance existing between the host and the foreign hematopoietic graft.

QUANTITATION OF TRANSPLANTATION IMMUNITY. I. METHOD

A technique for in vivo quantitation of transplantation immunity has been presented. Known numbers of H³-thymidine-labeled lymphoid cells were injected intravenously into isologous or homologous recipients. The total radioactivity in host spleens was counted at different time intervals. The rate of isotope disappearance from the spleen was exponential to 0.5 per cent of the dose or less. In isologous recipients, the calculated half-life of labeled cells was 82 hours; in homologous recipients it was 40 hours; and in presensitized homologous hosts it was 18 hours. The technique is a highly reproducible, precise, and sensitive measure of transplantation immunity.

Serological response of the bovine fetus to bovine viral diarrhea virus

Susceptible pregnant heifers were inoculated with bovine viral diarrhea virus at 150 days of gestation and earlier. Fetuses were surgically collected at selected times after inoculation. Serum immunoglobulins were quantitated, and the presence of specific antibodies was determined. In fetuses from heifers inoculated at 150 days, immunoglobulin M (IgM) appeared approximately 2 weeks after inoculation and was followed in 7 days by IgG1. Later IgG2 was detected in the sera of three fetuses. Serum-neutralizing and complement-fixing antibodies were first detected in a fetus taken at 206 days of gestation. Fetuses taken at later times also had specific serum antibodies. Possible explanations for the appearance of serum immunoglobulin substantially before specific bovine viral diarrhea antibodies include the viral alteration of host tissues rendering them antigenic viral activation of polyclonal B cells, and viral modulation of virus-specific lymphocytes causing specific interference with the appearance of antiviral antibodies. In one of the fetuses having IgG2, the serum also contained IgA. Placental leakage of material immunoglobulins was thought to be responsible for the presence of IgA and IgG2 in this fetus. Small quantities of IgM were found in the serum of two fetuses taken from heifers inoculated between 65 and 95 days of gestation, but specific antibodies were found in none.

Rotavirus infections in families. A clinical and virological study

Among 25 family members of 8 children with acute rotavirus gastroenteritis (8 siblings and 17 adults) gastroenteritis was recorded in 9 (5 siblings and 4 adults), and minor symptoms in 8 (2 siblings and 6 adults). A rotavirus infection was diagnosed in 7 of the family members with gastroenteritis and was probably the cause of the disease in the remaining 2 in this group. Four of the 8 family members with minor symptoms were infected with rotavirus, whereas no infection was detected among the 8 family members without symptoms. Serological findings sugggested that infants and young children underwent a primary infection with rotavirus, whereas older children and adults probably were reinfected. Adults as well as children with rotavirus infection excreted virus and may have served as sources of infection.

Investigations into the choice of immunogen, ligand, antiserum and assay conditions for the radioimmunoassay of conjugated cholic acid

Investigations into the choice of immunogen, ligand, antiserum and assay conditions for the radioimmunoassay of conjugated cholic acid have been performed with a view to producing optimal assay conditions. Cholic acid-BSA was found to be the best immunogen to produce antibodies to conjugated cholic acid and the response was of an IgG type. Incorporating a spacer (hexanoic acid) between hapten and carrier protein resulted in a decrease in antiserum titre. Optimal conditions for the assay were found using [125I]histamine-glycocholic acid as ligand with a dilution of antiserum to produce 60% binding of ligand and a pH of 7.4. Using these assay conditions no serum effects were found; extraction of serum prior to assay was therefore unnecessary. The assay was sensitive enough to detect post-prandial increased in serum bile acid concentrations following a liquid test meal; no increase was observed throughout the same time period in a fasting control.

Neutralization of animal viruses

Various aspects of the interaction of bacterial viruses and antibody were studied by Andrewes and Elford in England. Similar studies, as well as studies on animal viruses, were carried out in Australia by Burnet and his colleagues. One result of their extensive studies, which were summarized in great detail, was the conclusion that, with respect to their interaction with antibody, bacterial and animal viruses were basically different. Specifically, the difference resided in the stability of the union of virus and antibody, whereas bacterial viruses formed stable complexes, animal viruses formed complexes that tended to dissociate readily. The introduction of animal cell cultures as host systems greatly aided in the study of animal viruses, with respect to fewer and more readily controlled variables, and by the use of the plaque assay in enhanced quantitative reliability. In 1956, Dulbecco et al. described the interaction of two animal viruses with their respective antibodies. The results of these studies led these investigators to conclude, among other things, that animal viruses, at least the two they studied, reacted with antibodies to form complexes that did not dissociate spontaneously. This interpretation was challenged by Fazekas de St. Groth and Reid. As more animal virus-antibody systems were studied by many investigators, there seemed to be a greater accord for irreversible, rather than reversible, interaction. For this reason, in this chapter it is assumed that there are no differences between bacterial viruses, as one category, and animal viruses, as a separate category, concerning their interaction with antibodies. Rather, differences, when they exist, are considered to be related to the viruses per se. Although this chapter is intended to survey the neutralization of animal viruses, occasional reference is made to the studies on bacterial viruses when these studies are pertinent and illuminating to the topic at hand.

Rotavirus-associated gastroenteritis in two adults probably caused by virus reinfection

Rotavirus infection was diagnosed by virus detection and by serological methods in 2 women with acute gastroenteritis, aged 22 and 29 years, respectively. Both patients had been in close contact with children with rotavirus gastroenteritis. Rotavirus-specific antibodies were detected in serum specimens obtained prior to the illness in one of the patients, and the serological response in both patients suggested a reinfection with rotavirus as cause of the disease.

The immune response of zebu cattle infection with Trypanosoma congolense and T. vivax

Zebu cattle were infected with Trypanosoma congolense and T. vivax and changes in the levels of serum immunoglobulins were measured during infection and after treatment. Increases in the levels of IgM occurred within 14 days of infection coincidentally with the first appearance of trypanosomes in the peripheral blood. IgM levels rose to 2-10 times preinfection levels and remained high until the animals were treated with diminazene aceturate. Levels then declined to approximately pre-infection levels within 25 days. IgG levels showed little change. In one animal infected with T. congolense which died of trypanosomiasis, there was an initial increase in IgM levels but subsequently both IgM and IgG levels declined until the animal died. The neutralizing activity of whole serum, and serum IgM and IgG fractions from an ox infected with T. congolense were examined. High levels of neutralizing antibodies against trypanosomes isolated on the eighth day after infection were found in sera collected 12-29 days after infection. Most of the antibody activity was located in IgG fractions which showed a peak in neutralizing activity between day 17 and 22. IgG fractions of the sera showed only slight antibody activity.

Local antibody production in experimental pyelonephritis: amount, avidity, and immunoglobulin class

LOCAL ANTIBODY FORMATION IN INFECTED RABBIT KIDNEYS WAS STUDIED WITH THREE TECHNIQUES: the ammonium sulfate precipitation technique, the enzyme-linked immunosorbent assay, and by binding of newly synthesized (14)C-labeled antibodies to heat-killed bacteria. Local antibody was detected by day 11 of infection with all three techniques, and a significant correlation was found in titers by all three methods. In these studies, antibody synthesized early was in IgG and IgA class, whereas IgM antibodies appeared later (day 20) in the antibody response. No maturation of avidity of local antibody was noted with time. Since it was necessary to use different animals at each test occasion, individual differences in avidity could account for failure to note an increase in avidity with time.

Variations in the responses of C57BL-10J and A-J mice to sheep red blood cells

In response to repeated injections of sheep red blood cells, C57BL/10J mice produce predominantly 19S antibody in increasingly higher amounts, while A/J mice initially produce 19S antibody and then switch to produce increasing 7S antibody titers. In an F(1) generation all mice responded like the C57BL/10J mice. Backcross data implied genetic control involving at least three loci.

Antibody and immunoglobulin response to antirabies vaccination in man

Serum neutralization antibody and immunoglobulin responses in 30 individuals were studied in paired serum samples which had been obtained before and 2 to 3 weeks after the administration of a recall dose of rabies tissue culture vaccine. The immune reaction consisted of a predominantly immunoglobulin G (IgG) antibody response. Also, a significant increase in neutralizing antibody titers was observed, but without a consistently correlated change of the IgG levels in the individual serum samples. The radial immunodiffusion test appears to contain the elements necessary for the development of a routine test to determine rabies antibody in single serum samples.

Effect of -3-thienylalanine on antibody synthesis. V. Immunosuppression in mice by short diet and drug treatments

The analogue of phenylalanine, beta-3-thienylalanine, depresses severely the primary and secondary immune response to sheep erythrocytes in mice when administered for a few days immediately before and after each injection of antigen. For this immunosuppression to occur, animals must be maintained on a phenylalanine-free diet during the times of drug injection since dietary phenylalanine will restore anamnestic response. With these experimental conditions, the number of direct and indirect plaque-forming cells is greatly reduced during immune responses. The finding that marked immunosuppression can be obtained with a very short drug and diet treatment points to a potential usefullness of the analogue as a powerful immunosuppressant.

Serologic evidence that a herpes-type virus is the etiologic agent of heterophile-positive infectious mononucleosis

The antibody activity against herpes-type virus (HTV) of heterophile-positive infectious mononucleosis sera and "normal" sera from humans was determined with immunoferritin. The antiviral activity of the mononucleosis sera was associated with the IgM antibodies, while the antiviral activity of the "normal" human sera was associated with the IgG antibodies. It was concluded from these findings that the appearance of antibodies to herpes-type virus in heterophile-positive sera represents a primary immunogenic exposure to this virus, or to a serologically related virus. This conclusion, in turn, suggests that herpes-type virus or a serologically related virus is the etiologic agent of heterophile-positive mononucleosis.

Antibody Response to Bacterial Antigens: Characteristics of Antibody Response to Somatic Antigens of Salmonella typhimurium

The character of the antibody response in the rabbit to Salmonella typhimurium somatic (O) antigen was similar to the response to each of several serotypes of Shigella flexneri O antigens, namely a predominance of production of immunoglobulin M (IgM) antibody. Lipopolysaccharide protein (LPSP) and lipopolysaccharide (LPS) fractions of Salmonella O antigen differed significantly in both quantitative and qualitative aspects of their immunogenicity. LPSP elicited high levels of agglutinins and also induced the production of a significant amount of immunoglobulin G (IgG) antibody at a late period. LPS antigen elicited low levels of agglutinins which were exclusively IgM antibody. These results suggested that the chemical nature of the antigen is one important factor in the determination of the character of the antibody response. Further, it is suggested that the protein moiety of the O antigen complex is a carrier active in allowing induction of early IgM and of late IgG antibodies; in contrast, the lipid moiety may compete with this action of the carrier protein, thereby suppressing IgG antibody in the primary stage of the antibody-forming process.

Immunity to staphylococcal infection in mice: effect of living versus killed vaccine, role of circulating antibody, and induction of protection-inducing antigen(s) in vitro

Mice immunized by sublethal doses of living Staphylococcus aureus strains other than the Smith diffuse strain were significantly more resistant to challenge with the Smith diffuse strain than animals immunized with heat-killed organisms. The increased resistance observed was shown, by appropriate passive protection experiments with immune mouse sera, to be due to circulating antibody, probably of the IgM class. In addition, it was observed that strains of S. aureus other than the Smith diffuse strain, when cultured in a modified Staphylococcus 110 broth but not in Brain Heart Infusion, were capable of absorbing protective antibody from hyperimmune rabbit antiserum.

Immunoglobulins of cerebrospinal fluid in syphilis

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Human immunity to the meningococcus. II. Development of natural immunity

Results of the present study suggest that natural immunity to meningococcal disease is initiated, reinforced, and broadened by intermittent carriage of different strains of meningococci throughout life. In young adults, carriage of meningococci in the nasopharynx is an efficient process of immune sensitization. 92% of carriers of serogroup B, C, or Bo meningococci were found to develop increased titers of serum bactericidal activity to their own meningococcal isolate, and 87% developed bactericidal activity to heterologous strains of pathogenic meningococci. The rise in bactericidal titer occurred within 2 wk of onset of the carrier state, and was accompanied by an increase in titer of specific IgG, IgM, and IgA antibodies to meningococci. In early childhood, when few children have antibodies to pathogenic meningococci, active immunization seems to occur as a result of carriage of atypical, nonpathogenic strains. Immunity to systemic meningococcal infection among infants in the neonatal period is associated with the passive transfer of IgG antibodies from mother to fetus. The antigenic determinants which initiate the immune response to meningococci include the group-specific C polysaccharide, cross-reactive antigens, and type-specific antigens.