Cellular mechanisms of adjuvant action of bacterial lipopolysaccharide in anti-sheep red blood cell antibody response

In vivo production of various cytokines in splenocytes of sheep erythrocyte-immunized mice after intravenous administration of bacterial lipid A

The effects of an intravenous administration of lipid A from Salmonella minnesota R595 lipopolysaccharide on the in vivo production of interleukin-2 (IL-2), IL-4, IL-5 and IL-6 in the spleens of mice intravenously immunized with sheep red blood cell (SRBC) antigen were investigated. The increased number of antigen-specific IgM antibody-producing cells and the titer of the IgM serum antibody were measured using the plaque-forming cell (PFC) assay and an enzyme-linked immunosorbent assay (ELISA). Simultaneous injections of SRBC antigen and lipid A adjuvant enhanced IgM-PFC number on days 3 and 4 and the serum IgM titer on days 4 and 5 after the immunization. We found that the enhanced IL-4 and IL-5 levels correlated with the PFC number and IgM titer. When lipid A was injected intravenously 2 days after immunization with SRBC, the PFC number in lipid A-treated groups were similar to those in controls 3 and 4 days after the immunization. However, it was found that a twofold increase in the IgM titer in serum was induced by lipid A 5 days after immunization. In relation to this increase, lipid A stimulated the production of only IL-5 among the cytokines tested.

Comparison of murine B cell clonal expansions by synthetic lipid A and muramyl dipeptide analogs

Direct stimulations of murine B lymphocytes with synthetic lipid A analogs and synthetic muramyl dipeptide (MDP) derivatives were studied using a limiting dilution assay system. Synthetic lipid A analogs, GLA-27 and GLA-40, when conjugated with bovine serum albumin (BSA) had the ability to induce B cell clonal expansion of a single B cell from the spleen or bone-marrow. Their activities were almost the same as those of naturally obtained lipid A, but were lower than that of bacterial lipopolysaccharide (LPS). Addition of dextran sulfate (DXS) enhanced the effect of lipid A analogs. In contrast, synthetic MDP and its derivatives, although they had many biological and immunological activities in experimental animals, could not stimulate a single B cell to induce clonal expansion regardless of the presence or absence of DXS. These results suggested that lipid A analogs can directly cause the proliferation of B cells, but MDPs can not.

Immunological properties of Vibrio cholerae lipopolysaccharides

Immunological effects of wall lipopolysaccharide (LPS) preparations obtained from Vibrio cholerae Inaba 569B, Ogawa NIH 41 and NAG 4715 strains by the hot phenol-water procedure were examined in mice. Although these LPS lack KDO, which are basic components of the core region of most gram-negative LPS, they still have potencies as B-cell mitogens, adjuvants, immunosuppressants, polyclonal B-cell activators and phagocytic stimulants for macrophages. The activities of these V. cholerae LPS on murine immune system seemed to be weaker than those of Salmonella typhimurium LT2-LPS. Among these V. cholerae LPS, NAG 4715-LPS showed the strongest mitogenic activity and phagocytic stimulation, while the potencies of this NAG 4715-LPS for the induction of polyclonal B cell activation, adjuvant effects and immunosuppression did not seem to be greater to those of the other LPS.

Adjuvant action of capsular polysaccharide of Klebsiella pneumoniae on antibody response. V. Further biological properties of the active substance

The neutral fraction (neutral CPS-K) of Klebsiella pneumoniae capsular polysaccharide (CPS-K) from type 1, Kasuya strain, has already been reported as the active substance responsible for the strong adjuvant effect of CPS-K. The present results demonstrate that neutral CPS-K exhibits further common biological activities with lipopolysaccharide (LPS) isolated from Salmonella enteritidis. The intensity of the lethality in mice of neutral CPS-K by the intraperitoneal route is very similar to that of LPS. Its lethality for mice by the intravenous (i.v.) route is significantly stronger than that of LPS, because the degree of increase in the sensitivity to their lethality by i.v. challenge is smaller for LPS than for neutral CPS-K. The intensity of the pyrogenicity of neutral CPS-K in rabbits is approximately one-tenth of that of LPS as judged by the minimal pyrogenic doses and fever indices. The skin-preparatory potency of neutral CPS-K for the dermal Shwartzman phenomenon in rabbits is also approximately one-tenth of that of LPS compared on the basis of the minimal skin-preparatory doses. When injected i.v., neutral CPS-K exhibits a provocative effect on hemorrhagic reactions in skin sites prepared with neutral CPS-K or LPS.

Immunosuppressive effect of bacterial lipopolysaccharide on antibody response

Injection of endotoxins (bacterial lipopolysaccharide: LPS) several days prior to immunization causes the suppression of antibody response. The supressive effects of several kinds of LPS preparations on the plaque-forming cell (PFC) antibody response in the spleen of mice were examined after immunization with sheep red blood cells (SRBC). Glycolipids obtained from heptoseless mutants(Reform) of salmonella or its lipid A preparation coupled artificially with bovine serum albumin (BSA) are capable, like LPSobtained from a wild type (S form) strain, of inducing suppressionson of the PFC response, while alkaline-detoxified LPS can not. The refractory periods of the PFC response induced by LPS injection last only a few days. However, the use of cyclophosphamide (CY) together with LPS can extend the refractory periods of antigenic stimulation for several weeks. Injections of LPS andCY can also induce unresponsive states of OH agglutinin antibody response to antigenic stimulation with formalin-killed organisms of Escherichia coli or Salmonella enteritidis (presumably both thymus-independent antigens). These unresponsive states induced by LPS and CY are easily terminated by a transfer of syngeneic bone marrow cells but not by thymocyte transfer.

Effect of bacterial lipopolysaccharides on anti-trinitrophenyl antibody-producing cells. Nonspecific modification of the affinity at the cellular level

The effect of lipopolysaccharide (LPS) on anti-trinitrophenyl (TNP) direct plaque-forming cells (PFC) in the spleen of mice and the affinity of antibodies produced by these PFC were examined. Simultaneous injection of bacterial LPS and TNP-coupled sheep red blood cells(SRBC) induced an obvious increase in anti-TNP PFC numbers and heightened the antibody affinity at cellular levels. The higher the doses of LPS, the greater the effects. Concomitant injection of LPS in TNP-coupled homologous mouse red blood cells (MRBC) also elicited good anti-TNP PFC response and slightly heightened the affinity. Priming with LPS and SRBC together 7 days prior to immunization did not enhance the anti-TNP PFC response and it was difficult to alter the affinity. Preinjection with small amounts of TNP-MRBC or -rabbit red blood cells and LPS simultaneously did not induce any significant increase in anti-TNP PFC secondary response after reimmunization with TNP-SRBC, but obviously heightened the antibody affinity. Injection of LPS simultaneously with the secondary immunization was effective for both the anti-TNP PFC response and the alteration of antibody affinity. These results suggest that LPS affects the control mechanisms of anti-TNP antibody affinity via the non-thymus-derived helper cell function, and the adjuvant action and alteration of antibody affinity induced by LPS are regulated by different mechanisms.

Adjuvant effect of Bordetella pertussis vaccine to sheep erythrocytes: enhancement of antibody formation by using subcutaneous administration of adjuvant and antigen

The subcutaneous route (s.c.) was used to study the adjuvant effect of Bordetella pertussis vaccine (pv) on the primary antibody response to sheep erythrocytes. The reasons for using the s.c. route are discussed. PV, besides enhancing the hemagglutinin response, also markedly increased the number of plaque-forming cells in the draining lymph nodes. A heated preparation of PV was tested and found to possess significant adjuvant activity. Interestingly, the enhancement occurred in the absence of marked enlargement of the lymph nodes, which was characteristic of the unheated preparation. In addition, a crude solubilized cell-free preparation of PV was tested and also found to possess significant adjuvant activity. The activity was only partially abolished by heat. Hence, it was concluded that both heat-labile as well as heat-stable factors contributed to the adjuvanticity of PV. The studies also support the view that the draining lymph nodes represent a principal locus of action of PV and that the s.c. route of administration of adjuvant and antigen provides a suitable model for studying and assaying the adjuvanticity of PV.

Nonspecific elicitation of antibody-forming cells in the mouse spleen by bacterial lipopolysaccharide

Mechanisms of nonspecific elicitation of anti-sheep erythrocyte (SRBC) hemolytic antibody plaqueforming cells (PFC) in mouse spleens with an injection of bacterial endotoxin (lipopolysaccharide (LPS)) were studied in comparison with the genesis of naturally occurring "background" PFC in normal mouse spleens and of rapidly arising PFC in mouse spleens after immunization with SRBC. The cytokinetic pattern of anti-SRBC PFC response after an injection of LPS was quite different from that of the response elicited after immunization with SRBC. In addition, even though LPS nonspecifically elicited anti-SRBC PFC response in mice, LPS could not confer any immunological memory on mouse immunocytess for a "secondary-type" anti-SRBC PFC response to restimulation with LPS or SRBC. The administration of rabbit anti-mouse thymocyte immunoglobulin or anti-SRBC antiserum in mice markedly suppressed the PFC response after immunization with SRBC, but did not do so after stimulation with LPS. Neonatally thymectomized mice could still respond to stimulation with LPS, producing anti-SRBC PFC in their spleens. Injections of actinomycin D or cyclophosphamide into mice resulted in obvious reductions of the PFC responses elicited by either LPS or SRBC. However, injections of these immunosuppressive antisera or drugs did not affect the number of anti-SRBC PFC in normal mouse spleens. These results suggest that the genesis of anti-SRBC PFC developed under different conditions, i.e., background PFC, LPS-stimulated PFC, and antigen-stimulated PFC, are quite different from each other, and that the nonspecific elicitation of anti-SRBC PFC by LPS does not require the helper function of T lymphocytes. No obvious difference, however, was observed in the time of ontogenic maturation among these three different anti-SRBC PFC in the mouse spleens judging from when they were first manifested after birth.