Density of surface immunoglobulin and capping on rat B lymphocytes. I. Changes with aging

Acute phase protein levels and thymus, spleen and plasma protein synthesis rates differ in adult and old rats

Aging induces a dysregulation of immune and inflammation functions that may affect protein synthesis rates in lymphoid tissue and plasma proteins. We quantified in vivo synthesis rates of thymus, spleen and plasma proteins, including albumin and acute phase proteins, in adult (8 mo old) and old (22 mo old) rats using the flooding dose method [L-(1-(13)C) phenylalanine]. Immunosenescence was reflected by thymus atrophy and spleen hypertrophy in old rats but not in adult rats. A low albumin plasma level associated with high concentrations of fibrinogen, alpha(2)-macroglobulin, alpha(1)-acid glycoprotein and proteins other than albumin revealed a low grade inflammation in old rats. Protein fractional synthesis rates (FSR) and protein synthesis efficiencies of thymus were 29 and 26% lower in old than in adult rats, respectively; these variables did not differ in spleen. Protein absolute synthesis rates (ASR) of the thymus and spleen were 76% lower and 67% greater in old than adult rats, respectively. The FSR and ASR of albumin and other plasma proteins were greater in old than in adult rats. Protein synthesis measurement is a valuable nonimmunological tool to assess, in vivo, immune and inflammatory variables. Alterations in secondary lymphoid organs and plasma protein synthesis may contribute to the significant repartitioning of amino acids in old compared with adult rats and may be involved in sarcopenia.

Immunohistochemical analysis of ageing human B and T cell populations reveals an age-related decline of CD8 T cells in spleen but not gut-associated lymphoid tissue (GALT)

It is thought that senescence of the immune system is responsible, at least in part, for many health problems associated with ageing. Previous studies on changes in lymphocyte composition have used flow cytometry to study peripheral blood lymphocytes (PBL's), or cells isolated from rodent tissue, and have yielded conflicting results. We have used immunohistochemistry to determine whether the B and T cells in human tissue from spleen and gut are affected by age. Areas of germinal centre, mantle zone and marginal zone of B cell follicles were measured. In addition, CD4 and CD8 T cells in T cell areas and in B cell follicles were counted. We observed a striking age-related decrease in the proportion of CD8+ T cells in the T cell zones of the spleen. This decrease was not apparent in the T cell population that occupies splenic B cell areas, or in GALT. Further differences, in CD4+ cells, were seen between T cell populations in the T cell zones and those in B cell areas. These findings highlight differences between lymphocyte populations in different lymphoid tissues, and different compartments within each tissue, which may be of importance in future studies of the ageing immune system.

The effect of aging on the immune response: influence of phosphatidylcholine-containing lipid on IgD-receptor expression and antibody formation

It was reported previously that IgD-receptors (IgD-R) are expressed on both CD4+ and CD8+ human T cells and CD4+ murine T cells after exposure to oligomeric IgD, certain cytokines, or various pharmacological agents, as shown by rosetting with IgD-coated erythrocytes. Enhancement of antibody production is observed in mice after injection of oligomeric IgD and is mediated by these IgD-R+ T cells, while injection of monomeric IgD inhibits both IgD-R upregulation and augmentation of antibody responses induced by simultaneously injected oligomeric IgD. The effects of oligomeric IgD on IgD-R upregulation are lacking in aged mice. However, the oligomeric IgD induced enhanced antibody production can be transferred to aged mice with IgD-R+ T cells from young donors suggesting that the environment of the aged mouse supports the effector function of IgD-R+ T cells. We now report, in addition, that exposure to phosphatidylcholine (PC) and a PC-containing lipid mixture, AL721, is effective in causing IgD-R upregulation on T cells from both young and aged mice, and young humans. This effect can also be demonstrated in mice in vivo after administration of AL721. Moreover, this agent causes a two-fold enhancement of antibody production, as measured by PFC/spleen, to 4-hydroxy-5-iodo-3-nitrophenyl(acetyl)-Brucella abortus (NIP-BA) and NIP-horse red blood cells (RBC) in young and aged mice. There is no difference in the baseline membrane fluidity of lymphocytes from aged and young mice. Although PC causes an increase in membrane fluidity of lymphocytes from both young and old mice, and from humans, this effect on fluidity is not prevented by a protein kinase inhibitor, while PC's effect on IgD-R upregulation is prevented by the inhibitor. Moreover, no correlation was observed between IgD-R upregulation and membrane fluidity changes induced by AL721 administered in vivo. To evaluate the role of IgD-R induction in the augmentation of antibody production by phospholipids, the effect of monomeric IgD was investigated. The augmenting effect of AL721 on antibody production was prevented by a single injection of monomeric IgD at the time of antigen administration. We conclude that (1) PC-containing lipid mixtures are effective in enhancing antibody production in aged mice, (2) induction of IgD-R is responsible for the augmenting effects of AL721 on antibody production, and (3) monomeric IgD not only blocks the upregulation of IgD-R, as shown previously, but also the augmenting effect of previously upregulated IgD-R on T cells by preventing their interaction with surface IgD+ B cells.

Phenotypic and functional properties of B lymphocytes from aged mice

Phenotypic and functional properties of B lymphocytes from individual young and old mice of different inbred strains were studied. B lymphocyte subpopulations defined by the ratios of the densities of cell surface IgM and IgD were found to be altered with age. However, such alterations in B cell subsets were found only in 30-40% of the old mice. B cell mitogenic responses to anti-mu and anti-Lyb2 antibodies were decreased in a majority of DBA/2 mice. Proliferative responses to LPS and anti-mu were reduced only in a minority of CBA/Ca mice but there was a very good correlation in the responsiveness of the old mice to LPS and anti-mu. The anomalous properties of the individual old mice of these inbred strains may be due to a heterogeneity in the effects of aging or due to environmental influences.

Production of auto-anti-idiotype antibody during the normal immune response. XIV. Evidence for the antigen-independent operation of the idiotype network

We have previously shown that that idiotype (Id) repertoire expressed by old mice is different from that of young mice after immunization with trinitrophenylated Ficoll. Older mice also produce more auto-anti-Id antibodies than do young mice. Mice surviving a normally lethal dose of radiation (800 rads) as result of partial shielding of their bone marrow slowly recover immune function, after the repopulation of their peripheral lymphoid system by bone marrow precursor cells. Aged mice subjected to such a procedure produce low auto-anti-Id responses, like those of young mice. However, transfer of splenic T cells from old donors into such mice increases the magnitude of the auto-anti-Id response. In the present studies, we show that the age-related shift in Id expression is also determined by the age of the donor T cells. Furthermore, we show in serial cell transfer studies that the peripheral T-cell population of old mice modifies the level of the auto-anti-Id response in the absence of antigen. The results thus provide evidence for the normal, in vivo, operation of an Id-anti-Id network between B and T lymphocytes.

A specific defect in the proliferative capacity of B cells from old mice stimulated with autoreactive T cells

B lymphocytes from aged mice were found to be defective in their ability to proliferate in response to stimulation with an autoreactive T cell clone D1.4. The differentiative response leading to antibody secretion was also impaired in the auto D1.4 T cell-stimulated B cells from old mice in comparison to similarly stimulated B cells from young mice. The B cells from old mice were competent in activating the autoreactive T cells such that the T cells were induced to proliferate. The B cell defect appears to be restricted to a certain phase of B cell activation, since old mouse B cells responded to the auto D1.4 T cells by increasing cell surface Ia as well as size, but failed to incorporate tritiated thymidine. The responsiveness to interleukin-4 was found to be similar between B cells from young and old mice. It appeared that the B cells from old mice are specifically defective in progressing from the G0 phase of cell cycle into the S phase when stimulated with the auto D1.4 T cells.

Secretory immune responses in ageing rats. II. Phenotype distribution of lymphocytes in secretory and lymphoid tissues

The distribution of lymphocyte phenotypes was examined in various tissues from weanling (21-35 days), adult (3-4 months), mid-life (10-12 months) and senescent (18-20 months) rats. Lymphoid tissues included peripheral blood, spleen, cervical, mesenteric and inguinal lymph nodes. Tissues associated with secretory immune responses were also examined, including submandibular and parotid salivary glands, extraorbital lacrimal glands and Peyer's patches. IgA, IgG and IgM B cells were determined by surface Ig staining. Total T cells (W3/13), T helper/inducer (Th) (W3/25), T suppressor/cytotoxic (Ts) (OX8) and immature T cells (Thy 1.1; OX7) were also evaluated. IgG B cells were significantly decreased in lymphoid tissues from the senescent rats, while the weanling group exhibited decreased levels of all three B-cell isotypes compared to adult animals. IgA B cells were significantly decreased in the secretory tissues of the senescent rats, while IgM B cells were increased in both the weanling and senescent groups. Total T-cell percentages were unaffected by ageing in any of the tissues. The only consistent alteration in the lymphoid tissues was a decrease in Thy 1.1-positive cells in the older groups compared to the weanling group. A decreased Th cell percentage was demonstrated in the salivary and lacrimal glands of the weanling and senescent groups. Decreases in Th/Ts ratios, as well as decreased numbers of plasma cell precursors in the secretory tissues of the aged rats, suggests that alterations in normal secretory immune responses may be expected to accompany the ageing process.

Alterations in the human immune response to the hepatitis B vaccine among the elderly

The specific binding of hepatitis B (HBs) antigen by lymphocytes from old people immunized with hepatitis B vaccine was explored. For that purpose HBs antigen was combined with fluorescent microspheres, and labeled antigen was allowed to react with lymphocytes from HBs vaccine-responsive or unresponsive people. Lymphocytes from 10 responders and 14 nonresponders were tested for their antigen-binding ability. For controls, lymphocytes were incubated with microspheres bearing human albumin. Lymphocytes from 8 out of 10 responders were able to recognize HBs antigen; for the nonresponders the ratio was 9 out of 14. HBs-binding lymphocytes were B cells but not T lymphocytes. B and T cells from responders and nonresponders were combined and cultivated for 8 days in the presence of HBs antigen, and antibody-producing cells were counted. Neither B cells alone nor B cells plus T cells from nonresponders were able to produce antibody. On the other hand B cells from unresponsive old people produced antibodies when they were cultivated in the presence of HBs antigen and T cells from responsive old people. These data suggest that some elderly individuals who do not produce antibody after in vivo immunization by HBs vaccine do have antibody-producing cells. Instead of a gap in their immune repertoire, these people are suffering from immune dysfunction.

Human B-lymphocyte colony responses: suboptimal colony responsiveness in aged humans associated with defective function of B cells and monocytes

The abilities of human B cells from young and aged subjects to form colonies in semisolid cultures stimulated with Staphylococcus protein A were investigated. Approximately three-fourths of aged adults had significantly diminished colony responses compared to young adults. In 55% of these aged adults, the in vitro blocking of monocyte prostaglandin synthesis lead to a 1.5-fold or greater augmentation of the depressed colony responses. Other experiments showed that the improvement with indomethacin could not be explained by the greater sensitivity of aged versus young B-cell colony precursors to prostaglandin suppression. However, indomethacin failed to improve the depressed colony responses of the remaining aged adults. This failure could not be attributed to deficient interleukin 1 production, detectable alterations in accessory cell subsets of monocytes, or the lack of potential colony precursors bearing sIgD/M. Instead, the B cells from these aged subjects demonstrated a substantial decrease in the capping of sIgD/M compared to the B cells of aged subjects which displayed improved colony responses with indomethacin and compared to the B cells from young adults. Thus, these data indicate that the diminished B-cell colony responses of aged humans represent aberrancies within both the B-cell and monocyte lineages which might coexist.

Effects of aging on the lipid order and composition of rat adipocyte ghosts

An analysis of the cholesterol/phospholipid ratio of adipocyte ghosts from rat epididymal fat pads shows a significant increase with age (P less than 0.005). An attempt to correlate these changes with the order of the lipid matrix was made using the stearic acid spin label 2-(3-carboxypropyl)-4, 4-dimethyl-2-tridecyl-3-oxazolidinyloxyl [I(12,3)]. Although order was negatively correlated with temperature in preparations from both 6- and 24-month-old rats, no effect of age could be detected.

Lack of correlation between serum cholesterol levels, lymphocyte plasma membrane fluidity and mitogen responsiveness in young and aged chickens

Chickens were studied in an attempt to demonstrate correlations between serum lipid levels and peripheral blood lymphocyte (PBL) plasma membrane fluidity and mitogen responsiveness: (a) in the laying hen; (b) during aging; and (c) following dietary manipulation of serum cholesterol of young and aged chickens. The membrane fluidity of PBL from laying hens was significantly greater than that of immature birds. However, no direct correlation was found between serum lipid levels, nor the serum free cholesterol/phospholipid (FC/Pl) mole composition and PBL membrane fluidity in any of the age-groups tested. Likewise, no correlation was found either between serum FC/Pl mole ratio or membrane fluidity and mitogen responsiveness of PBL from birds up to 5 years of age nor was there any evidence for a decline in mitogen responsiveness up to this age. Supplementation of diets with 1% cholesterol induced hypercholesterolemia, mainly in the very low density lipoprotein (VLDL) fraction, but membrane fluidity and mitogen responsiveness remained unaffected.

Stability of E-rosettes in aged humans: effect of cytochalasin B and colchicine

A greater stability of E-rosettes and a reduced rate of capping of sheep erythrocytes are observed in elderly people. The lack of qualitative changes in the sensitivity of these processes to colchicine and cytochalasin B suggests that the function of the microfilaments and the microtubules is not primarily affected by ageing. The density and the affinity of the lymphocytes for sheep erythrocytes do not decrease in aged subjects. So the defective rearrangement of the E-receptors cannot be accounted for by some receptor alteration but points to a possible hindrance of their cross-linking in the membrane or their submembrane connection to the cytoskeleton.

Aging and the mucosal-associated lymphoid system

Several lines of evidence support the notion that the mucosal-associated lymphoid system differs from the systemic. It is possible that the mucosal lymphoid system may also differ from the systemic system with regard to immune competence with age. Our findings in these studies indicate a lack of age-associated immune dysfunction in the mucosal-associated lymph nodes: that is, mesenteric and mediastinal lymph node PFC responses of old mice that revealed no decline in magnitude were found to be highly heterogeneous with regard to antibody affinity and revealed no appreciable anti-idiotype-blocked, hapten-augmentable plaque-forming cells. By contrast, the number of splenic and, as well, draining peripheral lymph node IgM, IgG, and IgA anti-TNP PFC responses to TNP-BGG was found to decrease with age with a preferential loss of high affinity plaque-forming cells. This decline in immune activity in the systemic tissues coincided with the increased appearance of anti-idiotype-blocked, hapten-augmentable plaque-forming cells. This differential effect of aging on immune responses in vivo of mucosal and systemic lymphoid tissues imply a site preference for an age-related decline in immune function, and a division of the immune system into regulatory compartments during the normal immune response to antigen in old mice. The present demonstration of a differential effect of aging on immune function in vivo raises an important issue with regard to age-related host defense mechanisms. For example, it would seem reasonable to predict that if immune function totally wanes with age, old individuals would be greatly susceptible to disease and infection. On the contrary, host defense mechanisms relevant to infection show minimal alterations in healthy aged individuals. Thus, we believe that mucosal immunity may play a very important role in host defenses in elderly individuals.

Down's syndrome, aging, and Alzheimer's disease: a clinical review

This review has been directed towards those aspects of DS which bear upon pathological aging. Clinical dementia in DS has heretofore been studied largely by retrospective methods with variable findings. A prospective study utilizing techniques designed to measure cognitive performance in a poorly verbal, retarded population is badly needed. There is definitive evidence for Alzheimer's disease changes in the brains of DS patients with some suggestion of altered topography compared to the general population. Immunological studies have established a T-cell deficiency in DS that may be linked to precocious aging of thymic-dependent processes. Both antiviral and nonantiviral effects of interferon are accentuated in cell culture systems utilizing DS tissue, presumably as a consequence of the localization of the interferon gene(s) on chromosome 21. Multiple endocrine studies confirm the high frequency of autoimmune disease, an abnormality that may be related to the problems of immune surveillance in DS. Precocious aging has been noted in regards to measures of skin elasticity, fenestration of cardiac valves, and premature cataracts. The 21st chromosome has been implicated in the elevated activity of superoxide dismutase, a finding of significance in regard to potential intracellular damage from increased levels of peroxide. Several studies have suggested a compensatory increase in glutathione peroxidase.

Immunoregulation in senescence: increased inducibility of antigen-specific suppressor T cells and loss of cell sensitivity to immunosuppression in aging mice

Azobenzenearsonate (ABA)-specific T cell-mediated suppression has been studied in aging mice. ABA-specific suppressor T cells were induced in young and old mice by injection of ABA conjugated to syngeneic spleen cells (ABA-SC). These suppressor cells were tested for their ability to suppress the in vitro anti-trinitrophenyl (TNP) antibody response of lymph node cells obtained from ABA-keyhole limpet hemocyanin (KLH)-primed young or old mice and cultured with TNP-ABA-KLH. Suppressor T cells were found to be more easily induced in old than in young mice but to suppress less efficiently the antibody response of cells from old than from young mice. The increased inducibility of antigen-specific suppressor T cells in old mice is compatible with the age-dependent decline of immune responsiveness to exogenous antigens. The loss of cell sensitivity to antigen-specific immunosuppression as well as the lack of evidence for increased nonspecific suppression in old mice is consistent with the age-related increase in autoimmune disorders. These findings provide a unifying explanation for the most relevant immunological phenomena of senescence.

Detection of Raji binding activity in hyperimmune allogeneic tumor bearing sera associated with anti-BSA activity

Brown Norway (BN) rats were implanted twice with allogeneic (Lewis strain) Moloney sarcoma tumors (LM-2) and serum samples were assessed for Raji binding activity during primary and secondary tumor growth and rejection. Maximum Raji binding was observed 25 days after a primary tumor implant; thereafter, the binding activity decreased. Accelerated tumor rejection was observed after a second tumor implant and was associated with a 3-fold increase in serum Raji binding activity which remained elevated up to 40 days post-tumor implant. Raji binding activity in hyperimmune rats co-migrated with IgG in G-200 fractionated serum. Polyacrylamide gel electrophoresis (PAGE) revealed the presence of bovine serum albumin (BSA) on Raji cell membranes which reacted immunochemically with rabbit anti-BSA antiserum. Immunodiffusion studies revealed that sera from hyperimmune rats produced a precipitin band when reacted with Noniodet P-40 (NP-40) lysates of Raji cells and formed a line of identity with BSA.

Immune complexes with antiglobulin activity in sera of Moloney sarcoma-bearing rats

Immune complexes (IC) were detected and isolated from the serum of Brown Norway (BN), (Lewis x BN)F1, and Lewis rats bearing a Moloney sarcoma (MST). IC were isolated from the serum of individual rats employing a system of G-200 chromatography and passage through a heavy chain specific anti-rat IgG Immunoadsorbent. IgG and IgM were identified in the isolated IC by polyacrylamide gel electrophoresis (PAGE) and co-precipitation radioimmunoassays. Employing monospecific antibodies, IC consisting of IgG and IgM were bound to Raji cells as assessed by radioimmunoassay and indirect immunofluorescence. Raji binding activity of IC-containing serum was substantially reduced by pretreatment with dithiothreitol or incubation with anti-rat IgM or pooled normal rat IgG: F(ab')2. Sucrose density gradient ultracentrifugation under acid conditions dissociated IC into 7S IgG and 19S IgM components which recombined when co-incubated at pH 7 . 5. Viral antigens (gp70 and p30) were not detected in IC by PAGE and co-precipitation radioimmunoassay. Findings show that sera of rats bearing MST contain IC consisting predominantly of immunoglobulin. An IgM component which was separated, isolated and identified within IC containing serum displays anti-F(ab')2 reactivity.

Mobility of surface proteins on normal rat macrophages and on a "macrophagelike" rat tumor

Peritoneal macrophages endocytosed their histocompatibility antigens (RT1), Fc receptors (FcR), and concanavalin A (Con A) receptors after cross-linking by ligands, but did not cap these membrane proteins. The 323N cell, a "macrophage like" tumor cell, under identical conditions capped its surface proteins. Experiments measuring fluorescence recovery after photobleaching showed that the mobile fraction of RT1 was significantly greater in 323N cells than in normal peritoneal macrophages. Presumably, the membrane proteins of 323N are not as tethered to the cytoskeleton, or, if so, are in a nexus that is not the same as that which occurs between membrane proteins of normal macrophages and the cytoskeleton. The mobility of RT1 on normal lymphocytes was also different from that of macrophages. These observations suggest that the movement of membrane molecules is determined by cell type and is regulated by the cytoskeleton which varies in structure and function from cell type to cell type.

Cellular and molecular aspects of immune system aging

We begin with a brief discussion of the importance and advantages of immune studies to the problem of aging. This is followed by a short over-view of immune system aging at the systemic level. The major portion of the article is a review of observation, both at the cellular and molecular level, of changes in aging immune cells, with sections on intercellular communication, membrane phenomena, cyclic nucleotides, and molecular genetic changes.

Elimination of syngeneic sarcomas in rats by a subset of T lymphocytes

Established subcutaneous Moloney sarcomas (MST-1) of large size and long duration were eliminated from syngeneic rats by intravenous infusion of varying numbers of specific syngeneic effector T lymphocytes. Spleen cells from BN rats in which tumor had regressed were cultured in an in vitro mixed lymphocyte tumor cell culture (MLTC) to augment cytotoxicity of effector cells. In the MLTC a T cell subset was expanded in response to MST-1 antigens and transformed into blast elements. With these changes, there was an increase in the W3/25 antigen on the T cell surface, a decrease of W3/13 antigen, and an increase in the number of T cells with Ia antigens. The subset associated with elimination of established tumors was a blast T cell W3/25+, W3/13+, as detected by monoclonal antibodies to rat T antigens. The W3/25+ subset was poorly cytotoxic in vitro for MST-1 and apparently functioned in vivo as an amplifier or helper cell in the tumor-bearing host. The W3/25- population was a melange of cells that included (W3/13+, W3/25-) T cells, null cells, Ig+ cells, and macrophages, and was associated with enhancement of tumor in vivo, suggesting the presence of suppressor cells.

Permanent inhibition of capping of spleen lymphocytes from neonatally oestrogen-treated female mice

Female mice of the NMRI strain were injected with 5 microgram diethylstilboestrol (DES) or oestradiol-17 beta for the first 5 days after birth. Controls were given olive oil only. At the age of 4-6 months, the spleen lymphocyte population from the DES females had about half the percentage of cells undergoing capping after exposure to concanavalin A (Con A) as controls. The results from the oestradiol-injected females varied. After treatment of lymphocytes from DES females with colchicine, the percentage cells capping was as in control females. Binding studies did not reveal any difference in Con A receptor affinity or receptor number between DES females and controls.