Influence of the amount of antigen and the interval on the secondary reaction

The course of the revaccination reaction in mice immunized with different doses of sheep red blood cells was determined at different intervals after the primary stimulus. The maximum level of haemagglutinating antibodies in the secondary reaction was found after a high primary and secondary antigenic stimulus. On the contrary, if the level of haemolytic antibodies was determined, the higher was the primary antigenic stimulus, the lower was the secondary antibody response. Differences between haemagglutinins and haemolytic antibodies were also manifested in the earlier onset of the maximum haemolytic secondary reaction (five months after the first dose of antigen); the maximum haemagglutination response was not attained until eight months after the primary dose of antigen. The results comfirm that the basis of preparation for the secondary reaction is proliferation of immunologically activated Y cells; differences in the haemolytic and haemagglutination response are related to differences in the character of the antigenic determinants of sheep red cells.     

Neutralization of endogenous granulocyte-macrophage colony-stimulating factor subverts the protective immune response to Histoplasma capsulatum.

We examined the influence of endogenous GM-CSF on the course of primary and secondary pulmonary histoplasmosis. A high proportion (>/=75%) of C57BL/6 mice given mAb to GM-CSF did not survive primary infection, whereas 88-94% of infected controls survived. Analysis of leukocytes revealed significantly fewer CD4+ and CD8+ cells in lungs, but not airways, of anti-GM-CSF-treated mice as compared with infected controls. However, the histopathology was similar between the two groups. Lungs of mice given mAb to GM-CSF manifested depressed levels of TNF-alpha, IFN-gamma, and reactive nitrogen intermediates and elevated levels of IL-4 and IL-10. Administration of mAb to IL-4, to IL-10, or both restored protective immunity in GM-CSF-neutralized mice. In secondary infection, administration of mAb to GM-CSF exacerbated infection but did not alter survival over 30 days. The character of the inflammatory response was similar, and no differences were detected in Th1 or Th2 cytokine production between the two groups. Thus, endogenous GM-CSF is essential for survival in primary but not secondary infection, and blockade perturbs protective immunity. These findings reveal a new mechanism whereby GM-CSF contributes to host protection and demonstrate differences in control of primary and secondary histoplasmosis.     

Immune response in dog. 3. Antibody formation in dogs and rabbits to human serum proteins and keyhole limpet haemocyanin.

Antibody formation in dogs and rabbits to human serum proteins and keyhole limpet haemocyanin (KLH) following primary, secondary and multiple stimulation was analysed. Primary injection of human serum stimulates the formation of precipitin antibodies to beta2 lipoprotein in dogs, beta2 lipoprotein and beta globulin in rabbits. After a secondary dose the rabbits formed precipitins to a whole range of human serum proteins, while the dogs to beta2 lipoprotein, albumin, beta globulin. When the primary dose of antigen was divided over a period of 8 weeks, the dog produced precipitins to beta2 lipoprotein while the rabbit to a wide range of serum proteins. Secondary stimulation of these animals did not increase the number of precipitins formed. Quantitative analysis of the antibody produced show that the best response was with beta2 lipoprotein followed by albumin and beta globulin. As the immunogenicity of the antigen was greater the differences between the two species were narrow. These differences were less pronounced following the primary injection than after the secondary and multiple stimulations. The primary response to KLH (which represents mainly IgM) is better in the dog than in the rabbit, while the secondary response (IgG) was better in the rabbit. The poorer IgG response in the dog compared to the rabbit, observed in all the experiments, is discussed.     

Protective immunity and delayed type hypersensitivity reaction are uncoupled in experimental Leishmania major infection of CCR6-negative mice

The chemokine receptor CCR6 is expressed on naïve B cells, dendritic cell and T-cell subpopulations and is involved in cell navigation during organogenesis and recruitment in response to inflammatory stimuli. Gene-deficient C57BL/6 CCR6^−/− mice infected with the protozoan parasite Leishmania (L.) major were able to mount a protective immune response and survived the infection. Whereas macrophage production of nitric oxide (NO), the key leishmanicidal effector molecule during the immune response to L. major, did not require CCR6, the migration of CD4⁺ T cells to the site of infection was reduced in CCR6^−/− mice. Furthermore, the induction of a T-cell-dependent delayed-type-hypersensitivity (DTH) reaction was defective in CCR6^−/− mice, whereas resistance to re-infection was maintained in the absence of CCR6. We conclude that CCR6 contributes to the recruitment of T cells to the site of infection, but is largely dispensable for the control of L. major parasites during primary or secondary infection.     

Immune response in malnutrition. Differential effect of dietary protein restriction on the IgM and IgG response to alloantigens

The capacity for humoral immune response was evaluated in C57BL/6 mice fed diets with low (8%) or normal (27%) protein content upon primary and secondary stimulation with allogeneic cells from the DBA/2 strain. Primary antibody response was assessed by titration of serum hemagglutinins and by quantitation of direct plaque forming cells (PFC) in immune spleen suspensions, with lymphoma cells L5178Y of the DBA/2 strain as target. Secondary antibody response was assessed by titration of serum hemagglutinins. The following results were obtained: 1) Significant decrease in the total number of spleen cells was observed in protein deficient animals while the numbers of IgM PFC/spleen did show small reduction. 2) The number of direct alloantibody PFC/10⁷ spleen cells was increased in the protein deficient animals in comparison to the normally fed controls. 3) The above effect was observed even after short periods (1 week) of protein depletion. 4) Titers of serum hemagglutinins in protein deficient mice were similar or higher than in normal mice during the primary response but markedly depressed during the secondary response. 5) The synthesis of IgG hemagglutinins was depressed in protein deficient mice during both the primary and secondary responses. The results indicated that cells producing IgM alloantibodies are not affected by protein deficiency starting during the fourth week of age, while one or more of the cell populations interacting in the IgG response to alloantigens is markedly depressed by similar protein restriction. It was suggested also that protein deficient animals present a failure in the regulatory mechanism(s) of the IgM response to alloantigens.     

Adjuvant Action of Capsular Polysaccharide of Klebsiella pneumoniae on Antibody Response

A study was performed to clarify the roles of primary and secondary injections of antigen and adjuvant (capsular polysaccharide of Klebsiella pneumoniae, CPS-K) in induction of antibody responses and in development of immunological memory in mice to bovine serum albumin (BSA). A primary injecion of BSA alone neither induced significant primary antibody response nor increased immunological memory for a secondary antibody response but, if primary injections of BSA and CPS-K were performed simultaneously, high antibody responses were induced. Moreover, a prior injection of BSA alone or CPS-K alone decreased the level of primary antibody response and the degree of increase in memory following the subsequent injection of BSA mixed with CPS-K. In contrast, a secondary injection of BSA alone into mice once primed with a mixture of BSA and CPS-K elicited very high secondary type antibody response and increased secondarily the memory for a tertiary antibody response. Injection of CPS-K simultaneously with or shortly before or after the secondary injection of BSA did not increase the level of the secondary antibody response and the degree of the secondary increase in memory. Augmentation of the secondary antibody response was elicited by simultaneous injection of CPS-K only when the secondary response was induced inadequately by a suboptimum or supraoptimum dose of antigen.     

CD4-positive T lymphocytes are required for the generation of the primary but not the secondary CD8-positive cytolytic T lymphocyte response to herpes simplex virus in C57BL/6 mice.

To understand the cellular basis for recovery from HSV infection, it is critical to identify functional interactions between HSV-specific T lymphocyte subpopulations involved in the generation of the optimal response. To this end, the requirement for CD4+ (L3T4+) T lymphocytes in the development of the primary and secondary CD8+ (Lyt-2+) cytolytic T lymphocyte (CTL) response following HSV infection in C57BL/6 mice was investigated. It was found that chronic depletion of CD4+ cells in vivo by treatment with the mAb GK1.5, which resulted in greater than 95% depletion of peripheral CD4+ T lymphocytes in treated animals, caused a profound decrease in the levels of cytolytic activity obtained during the primary response in the draining popliteal lymph nodes of mice responding to infection in the hind footpads. However, treatment did not affect the levels of in vivo secondary CTL activity in the popliteal lymph nodes, nor the in vitro secondary response in the spleen. The decreased CTL activity observed during the primary response was not due to an inability to prime HSV-specific CTL precursors (CTLp), as full cytolytic activity was obtained following culture of lymphocytes in the presence of exogenous IL-2 and antigen, and the response could be reconstituted by treatment with recombinant IL-2 in vivo. Analysis of the secondary CTL response in the spleen indicated that CD4+ cells were not required for either the generation or maintenance of this aspect of the response. However, blockade of IL-2 utilization by CTL using anti-IL-2R antibodies indicated that this lymphokine was absolutely essential for secondary CTL expansion in vitro. Finally, mice that had been infected 12 months previously exhibited a decreased ability to generate secondary HSV-specific CTL in vitro following CD4-depletion in vivo. Taken together, these results suggest two distinct stages of CTL development during the response: an early primary stage dependent upon the presence of CD4+ cells, and a later, CD4-independent stage operative during the secondary response, which decays with time postinfection.     

Carrier-induced tolerance to nucleic acid antigens.

BALB/c and SJL mice were treated with nucleosides-IgG1 as a tolerogen, before either primary or secondary immunization with nucleosides-keyhole limpet hemocyanin. Nucleoside-specific responses were measured serologically by a modified Farr assay, with either 14C-labeled denatured DNA or nucleosides-131-I-labeled BSA as test antigen. Specificity of the response was tested by hapten inhition experiments. Multiple doses of nucleosides-IgG1 tolerogen given before the primary or secondary immunization effectively suppressed the secondary and tertiary anti-nucleoside responses. The tolerogen did not suppress the response to an unrelated hapten-KLH conjugate. The IgG alone did not suppress the anti-nucleoside response of BALB/c mice to nucleosides-KLH. Single doses of tolerogen before the primary or secondary immunization were less effective. Residual antibody in partially suppressed BALB/c mice showed changes in specificity as compared to controls. Suppression of the secondary response of SJL mice was measured much more readily by binding of nucleosides-131-I-BSA than by binding of denatured DNA. This reflected an altered specificity of the residual antibody; in control animals, antibodies were directed against all four nucleosides, whereas the antibodies of partially suppressed animals were directed only against guanosine. Suppression of anti-nucleic acid antibody responses may have therapeutic application in the management of systemic lupus erythematosus.     

Immune response in dog 2 effect of dose of antigen on antibody production.

The primary antibody response of dogs and rabbits to both 'H' and 'O' antigens of Salmonella typhosa following intravenous injection with a formalin killed vaccine from 2.4 x 10(6) to 2.4 x 10(10) organisms/kg body weight was analysed. The animals were restimulated 80 days later with various vaccine concentrations. The lgM anti-'O' and lgG anti-'H' and 'O' antigens in the dogs, were significantly weaker in both primary and secondary response than the comparable rabbit group. Primary lgM anti-'H' response in the dog was found to be greater, equal, or less than that observed in the rabbit. A closer analysis of the primary response indicated that both animal species show the same latent period and doubling time in respect of anti-'H', and the differences observed are probably the result of the number of progenitor cells stimulated by the antigen. On the other hand the suppressed response of the dog to 'O'-antigen is the result of an overall weaker response of this animal to the antigen. The secondary anti-'H' lgM response was found to be greater than, equal to, or less than the primary response in the same animal. The significant inhibition of this response was observed in those animals which received a high primary dose of antigen.     

The intestinal mast cell response to Trichinella spiralis infection in mast cell-deficient w/wv mice

The intestinal mast cell response and lymphoblast activity, as measured by the incorporation of 3H-thymidine into mesenteric lymph node cells (MLN) of WBB6F1-w/wv(w/wv) mice, their normal congenic littermates (+/+) and C57BL/6J mice, were compared after infection with Trichinella spiralis. Marked and similar blast cell activity and an increase in number of cells were observed in the MLN of infected w/wv and C57BL/6J mice 7 and 15 days P.I. In contrast to C57BL/6J mice, primary T. spiralis intestinal infections were prolonged in w/wv mice and more muscle larvae were recovered from w/wv mice 29 days post-infection. In C57BL/6J mice mucosal mast cell (MMC) numbers increased on day 7 P.I. whereas in w/wv mice these cells did not increase significantly until day 15 post-infection, reaching a peak on day 22. In w/wv mice, the response to secondary infection as determined by an accelerated expulsion of adult worms did not occur until day 11 postchallenge whereas in +/+ and C57BL/6J mice worm expulsion was nearly complete at that time. In both primary and secondary infections, the MMC numbers in w/wv mice were significantly lower than in C57BL/6J or +/+ mice. The results suggest that prolongation of T. spiralis infection in w/wv mice is associated with delayed appearance of mast cells in the intestinal mucosa which may reflect slow generation of the intestinal inflammatory response.     

Differential immunosuppressive effects of ascites fluid from mastocytoma-bearing mice on primary vs secondary immunocyte responses.

The effects of immunosuppressive ascites fluids from mastocytoma-bearing mice on the primary vs secondary immune response to sheep red blood cells (SRBC) was examined. Injection of mice with ascites fluid from tumor-bearing mice markedly depressed the primary immune response of normal syngeneic mice challenged with SRBC. However, there was a preferential depression of the 19S IgM antibody response as compared with the 7S IgG response. Injection of ascites fluid shortly before secondary immunization of mice with SRBC also resulted in depressed IgM PFC responses but only a slight to moderate depression of IgG PFC. Treatment of mice with the ascites fluid before primary immunization had little if any effect on the secondary IgG PFC response, although the IgM response was moderately depressed. These results indicate that the immunosuppressive factor(s) present in the ascites fluid of mastocytoma-bearing mice has a differential effect on distinct classes of immunocytes. Those immunocytes or their precursors involved in formation of low efficiency 7S IgG antibody are more resistant to immunodepression. Such differences appear due to different sensitivities of cells involved in the immune response system.     

Immune Response against Hamster Erythrocytes in the Low-Responder Mouse Strains

Antibody response against hamster red blood cells (H-RBC) was examined in inbred strains of C57BL/6, AKR, C3H/He, DDD and SL mice, and outbred CF1 mice. 1) There were strain differences in antibody response after a primary intravenous injection of H-RBC. DDD, SL and CF1 mice belonged to high-responder strains, while C57BL/6, AKR and C3H/He to low-responder strains. In the spleens of immunized CF1 and SL, 40 to 70 times as many plaque-forming cells (PFC) as those in C57BL/6 mice were detected. The magnitudes of the response were: CF1 ≒ SL>DDD>>C3H/He ? AKR>C57BL/6. 2) 2-mercaptoethanol resistant (MER) antibody was detected in neither low- nor high-responders after a primary intravenous antigen-injection. 3) After a secondary intravenous antigen-injection, MER antibody was detected in all the SL mice, but only in 30 to 50% of AKR and C57BL/6 mice. 4) A subcutaneous injection of H-RBC in Freund's complete adjuvant (FCA) did not elicit antibody production within 10 days. When mice pre-sensitized 7 days in advance w^Tith H-RBC in FCA were intravenously injected with H-RBC, enhanced antibody production of the primary type was observed in all the mouse strains. 5) In pre-sensitized mice, the extent of the enhancement of antibody production was the highest in low-responder C57BL/6 mice and the lowest in high-responder SL and CF1 strains. Thus, there was no strain difference in antibody titers or the numbers of PFC after the booster.     

Immunity to tapeworms: acquired resistance to Hymenolepis citelli in the mouse

The dynamics of secondary infections with Hymenolepis citelli in mice are described. A primary infection of one and six cysticercoids for 21 days sensitized CFLP male mice against homologous challenge infections. Acquired resistance was manifested mainly as stunting/destrobilation of secondary worms. The severity of stunting depended on the intensity of the primary infection. Secondary worms were not expelled more rapidly than primary worms but the protective response retards growth early in challenge infections. Sensitization of mice for seven days with six or 24 cysticercoids did not confer a measurable protective response, whereas priming by the same regime for 21 days induced a significant protective response. Acquired resistance to challenge waned with time in the absence of the primary worms. The growth and survival of a six-cysticercoid primary infection was enhanced by the administration of the immunosuppressant drug cortisone acetate. Worms from cortisone-treated mice were heavier than those from untreated controls. Acquired resistance to homologous challenge was also partially ablated in cortisone-treated mice. It is suggested that rejection of primary infections and stunting/destrobilation of secondary worms may be immunologically mediated.     

IL-10 is required for optimal CD8 T cell memory following Listeria monocytogenes infection

IL-10 is an important immunoregulatory cytokine that plays a central role in maintaining a balance between protective immunity against infection and limiting proinflammatory responses to self or cross-reactive Ags. We examined the full effects of IL-10 deficiency on the establishment and quality of T cell memory using murine listeriosis as a model system. IL-10(-/-) mice had reduced bacterial loads and a shorter duration of primary infection than did wild-type mice. However, the number of Ag-specific T cells in secondary lymphoid and nonlymphoid organs was diminished in IL-10(-/-) mice, compared with wild-type mice, at the peak of the effector response. Moreover, the frequency and protective capacity of memory T cells also were reduced in IL-10(-/-) mice when assessed up to 100 days postinfection. Remarkably, this effect was more pronounced for CD8 T cells than CD4 T cells. To address whether differences in the number of bacteria and duration of primary infection could explain these findings, both strains of mice were treated with ampicillin 24 hours after primary infection. Despite there being more comparable bacterial loads during primary infection, IL-10(-/-) mice still generated fewer memory CD8 T cells and were less protected against secondary infection than were wild-type mice. Finally, the adoptive transfer of purified CD8 T cells from previously infected wild-type mice into naive recipients conferred better protection than the transfer of CD8 T cells from immune IL-10(-/-) mice. Overall, these data show that IL-10 plays an unexpected role in promoting and/or sustaining CD8 T cell memory following Listeria monocytogenes infection.     

Anti-tumor necrosis factor antibodies suppress cell-mediated immunity in vivo.

Rabbit anti-murine TNF-alpha antibodies were administered in vivo to mice to evaluate the role of TNF-alpha in T cell-mediated immunity. Anti-TNF suppressed the in vivo development of contact sensitivity to the hapten TNP in a dose-dependent fashion. Similarly anti-TNF suppressed the in vivo priming for TNP-specific CTL. Control antibodies did not suppress cell-mediated immunity, whereas purified murine rTNF-alpha neutralized the antibody activity. Antibody therapy was effective during the afferent or priming limb of immunity, but could not inhibit the response if administered during the efferent limb. FACS for CD2, CD3, CD4, and CD8 T, B, and NK cell surface markers demonstrated no major change in the distribution of splenic lymphoid cell populations in animals pretreated with anti-TNF antibody. These results suggest that anti-TNF antibody may be interfering with soluble cytokines rather than with cell surface TNF causing depletion of cell populations. In vitro analyses also showed that anti-TNF has minimal inhibitory effects on secondary (secondary CTL) or strong primary (primary CTL, alpha CD3, MLR) responses, even though these in vitro cultures produce TNF mRNA as shown by polymerase chain reaction amplification. Although anti-TNF antibody did not affect the above responses, primary interactions are strongly inhibited in vivo. These findings suggest that TNF is important during afferent, priming events in immunity and that inhibition of TNF receptor-ligand interactions may alter immunity early in a response. Conversely such inhibition is ineffective later in a response, perhaps due to the ability of multiple other receptor-ligand pathways to bypass TNF.     

Effect of total lymphoid irradiation (TLI) on the primary and secondary antibody response to sheep red blood cells.

The effect of total lymphoid irradiation (TLI) on the primary and secondary hemagglutinin response to sheep red blood cells (SRBC) was studied in BALB/c mice. The primary response was eliminated for 1 month and began to return by Day 44. The latter response was IgM, and the IgG response did not return until approximately 200 days after TLI. The prolonged immunosuppression required inclusion of the thymus in the radiation field. Mice treated with single-dose whole-body irradiation (WBI) regained a normal IgG response within 28 days after irradiation. Immunization of mice prior to treatment with TLI or WBI resulted in a vigorous IgG response when mice were boosted 1 month after irradiation.     

Ontogenetic development of antibody formation in response to different doses of gram-negative microorganisms in young rabbits

Newborn and 15-day-old rabbits were immunized with different doses of heat-inactivated suspension ofEscherichia coli andSalmonella paralyphi B. The secondary immunization was performed after 4 weeks and the dynamics, magnitude and site of the secondary response studied. The magnitude of the secondary response was found to depend on the magnitude and rate of the primary response, this latter reflecting the dose used. A direct relationship was found in the range of the minimal and optimal dose: the higher the primary dose the higher the secondary response. After a rapid and pronounced primary response evoked by a high dose of 10¹⁰ microorganisms in 15-day-old rabbits, a partial inhibition of the secondary response was observed. The inhibition was pronounced primarily in the spleen; the lymphatic nodes reacted by a higher number of antibody producing cells as compared with the control nonprimed young rabbits.     

Cell-mediated cytotoxicity: comparison of primary and secondary immune reactions after parainfluenza type 1 virus inoculation.

H-2 antigen compatibility of effector spleen cells and target cells was necessary for cell-mediated cytotoxicity (CMC) after both 1 and 2 intraperitoneal inoculation of 6/94 virus into mice. T cells were responsible for both primary and secondary CMS reactions. Neither reaction was influenced by the presence of virus-specific antibody added to the test system. Secondary CMC peaked earlier than the primary response and declined more rapidly. In vitro stimulation of primed spleen cells could also be used to detect the secondary CMC response.     

Delayed advent of stringent, non-H-2 genetic regulation of the antibody response to a protein antigen.

The role of non-H-2 gene(s) in the control of the antibody response to three lysozymes was investigated. Upon secondary challenge, A/J (H-2a) mice generated at least a 25-fold greater anti-lysozyme plaque-forming cell response than did B10.A (H-2a) mice. Nearly equal, strong peak primary responses, predominantly IgG in nature, were obtained from both A/J and B10.A mice after a single challenge with lysozyme in complete Freund's adjuvant. However, clear differences in responses are seen within 5 days after the peak primary plaque-forming response and by day 28 at the serum antibody level. B10.A mice never equal their primary responses, whereas A/J mice demonstrate positive immune memory. It appears that a non-H-2 gene(s) that regulates the overall antibody level to a protein antigen becomes manifest only after an initial antibody response.     

Facing two T cell epitopes: a degree of randomness in the primary response is lost upon secondary immunization

We have analyzed the hierarchy of epitope-specific T cell populations during a primary and a secondary CD8 T cell response. MHC-peptide tetramers were used to track the in vivo kinetics of expansion of T cell populations specific for two Kd-restricted epitopes simultaneously presented by a murine tumor cell following primary or recall immunizations. Individual syngeneic mice generated remarkably different primary CTL responses, as reflected by up to 60-fold differences in the relative contribution of each peptide-specific T cell population to the overall response. In these primary immunizations, the CTL dominance was not dictated by the respective abundance of the presented epitopes. In sharp contrast, the secondary response was systematically associated with a selective expansion of the same epitope-specific population both in vitro and in vivo. In vitro experiments indicated that the extent of expansion of each epitope-specific memory population is modulated by the epitope density. We conclude that, at least for this set of epitopes, the CTL hierarchy is not controlled by the same parameters in a primary vs a secondary response.