The bone marrow as a site of antibody production after a mucosal immunization

Kinetics and type of immune response following intranasal and subcutaneous immunisation of calves

Protection of animals against respiratory infections has long been known to depend on respiratory mucosal immunity. However, few studies have been reported on the immune response following intranasal (i.n.) immunisation with non-living, soluble antigens. This study determined the kinetics of the humoral and cellular immune responses in calves after i.n. immunisation with Limulus haemocyanin (LH) with cholera toxin adjuvant, or subcutaneous (s.c.) immunisation with LH in incomplete Freund's adjuvant. A proliferative response of peripheral blood mononuclear cells cultured in vitro with LH was observed in animals immunised 7-10 days after i.n. and s.c. immunisations with no significant differences between the two immunised groups. LH -specific antibody was present in the serum of animals immunised s.c. (IgM, IgG1 and IgG2) and i.n. (IgA). Although significant IgA responses were observed, i.n. immunisations in cattle with soluble protein antigens and cholera toxin as an adjuvant did not induce a strong systemic immune response.

Priming or tolerization of the B- and Th2-dependent immune response by the oral administration of OVA-DNP is determined by the antigen dosage

In the present report we established antigen dosages that induce oral tolerance of Th1 and Th2 lymphocytes or instead prime B- and Th2-dependent immune response and induce the tolerance of Th1 lymphocytes. Using different hapten-carrier systems, we found that low doses of OVA-DNP administered orally primed B and Th2 cells. On the other hand, no priming of B or Th2 cells was found in high-dose-OVA-DNP-fed rats. Low-dose-OVA-DNP-fed rats showed a strong mucosal immune response, with a high number of IgA anti-DNP antibody-forming cells in the lamina propria, while no mucosal immune response was observed in high-dose-OVA-DNP-fed rats. Thirty days after the immunization, tolerization of Th1 lymphocytes was confirmed in low- and high-dose-OVA-DNP-fed rats by diminished antigen-specific proliferation in vitro, reduced titers of anti-DNP IgG2a in serum, reduced expression of CD25 and CD134 molecules in cultured cells exposed to the antigen, reduced DTH reaction, and reduced IL-2 synthesis in culture. On the other hand, a high dose of OVA-DNP led to Th1 and Th2 tolerance, with an inhibition of specific IgG1 and IgG2a anti-DNP antibodies in serum after a parenteral challenge with OVA in CFA. This functional evidence was supported by the direct examination of IL-2 and IL-4 production. Furthermore, whereas in vitro assays seem to indicate that active suppression could be the responsible for Th1 tolerization in low-dose-OVA-DNP-fed rats, the results obtained after the transference of spleen or MLN cells to naive recipients support the idea that a subtractive mechanism is behind the tolerization of Th1 lymphocytes.

Long-term antibodies after an oral immunization with cholera toxin are synthesized in the bone marrow and may play a role in the regulation of memory B-cell maintenance at systemic and mucosal sites

To study the importance of the bone marrow in the long-term antibody response, IgG and IgA antitoxin antibody-forming cells were evaluated by ELISPOT in Peyer's patches, mesenteric lymph nodes, spleen, lamina propria of the small intestine and bone marrow at several times after oral immunization with cholera toxin. The mesenteric lymph node was the site having the major frequency of IgG antitoxin during the first two weeks after priming, whereas lamina propria was the site with a major number of IgA antitoxin antibody-forming cells. However, from 3 weeks until 10 months after priming, bone marrow became the site with the major frequency of IgG, and especially IgA antitoxin antibody-forming cells (without taking into account the lamina propria). This result indicates that bone marrow was responsible for the long-term antibody response and raises questions concerning the mechanisms involved in the maintenance of antibody production. The importance of bone marrow as a site of antibody production was great when we analysed results as the true contribution of the total number of antitoxin antibody-forming cells, taking into account the number of cells recovered from each organ. When we analysed the anatomical location of memory B and T cells by adoptive transference, we found that cells from mesenteric lymph nodes and spleen were able to transfer a strong antibody response to naive syngeneic recipients, whereas bone marrow cells transferred a weak antibody response.

Oral administration of one dose of cholera toxin induces a systemic immune response prior to a mucosal immune response by a direct presentation in the spleen

In the present report the results indicate that the oral administration of one dose of CT in rats results in an antibody immune response in the spleen 48 h later, whereas no antitoxin antibody forming cells were found in the Peyer patches (PP), mesenteric lymph node (MLN) and lamina propria (LP) of the small intestine. At this time the main isotype of the antitoxin antibodies in the spleen were IgG and IgM, 5 days after the priming, few antitoxin AFC were observed in the MLN, IgG being the main isotype, whereas no IgM antitoxin AFC were found. At 1 week after priming the number of antitoxin AFC in the MLN reached similar values to those observed in the spleen. When cells from the spleen of rats primed orally with one dose of CT were cultured during 4 days in the presence of inhibitory doses of anti-Ia MAb (OX6), the number of antitoxin AFC was diminished when compared with that observed when cells were cultured in the absence of anti-Ia. The main isotype of antitoxin AFC observed when cells were analyzed after culture was IgM and it was the isotype most affected by the treatment with MAb anti-Ia. These results strongly suggest that an in situ presentation of the antigen did occur in the spleen. On the other hand, when the secondary immune response was studied 48 h after boosting, antitoxin AFC were found in the PP, MLN, SP and LP and 5 days after the booster a 20-30-fold increase was observed in all lymphoid tissues studied, indicating that the secondary immune response found in the spleen was mainly due to the recruitment of memory cells from Peyer's patches. However, when spleen cells were cultured 48 h after the immunization in the presence of inhibitory doses of anti-Ia a little decrease in the number of AFC was observed when compared with the controls (in absence of anti-Ia). The analysis of the antitoxin antibodies in sera and intestinal fluids were in line with the results presented above. The results shown in this report indicate that the systemic immune response observed after the oral administration of CT could be due in part to an in situ presentation of the antigen in the systemic compartments, especially in the spleen.

Poliovirus-specific immunoglobulin A in persons vaccinated with inactivated poliovirus vaccine in The Netherlands

In The Netherlands the inactivated poliovirus vaccine (IPV) is used for protection against poliomyelitis. It is not clear if parenteral vaccination with IPV can lead to priming of the mucosal immune system. We developed and evaluated enzyme-linked immunosorbent assays for the detection of poliovirus serotype-specific immunoglobulin A (IgA) and secretory IgA antibodies. Using these assays we examined the kinetics of the IgA response in sequential serum samples from 15 poliomyelitis patients after natural infection with serotype 3 poliovirus. In 36% of the patients IgA remained present for up to 5 months postinfection. Furthermore, we examined, in an IPV-vaccinated population, the presence of IgA antibodies in sera from young children (4 to 12 years of age; n = 177), sera from older children (between 13 and 15 years of age; n = 123), sera from healthy blood donors (n = 66), and sera from naturally immune elderly persons (n = 54). The seroprevalence of IgA to all three serotypes was low in young vaccinated children (5 to 7%), and the seroprevalence of IgA types 2 and 3 was low in older vaccinated children (2 to 3%). The seroprevalence of antibodies to type 1 was significantly higher (18%) in older children than in younger children. This higher seroprevalence is most likely explained by the persistence of IgA following infection with the serotype 1 wild-type poliovirus strain during the 1978 epidemic. In healthy adults, the seroprevalence of type 1- and type 2-specific IgA was significantly higher than that in young children. These results suggest that at least part of the IgA found in the older population is induced by infections unrelated to the IPV vaccination schedule. Finally, we found that parenteral vaccination with IPV was able to boost secretory IgA responses in 74 to 87% of a naturally exposed elderly population (n = 54). While the presence of secretory IgA in IPV-vaccinated persons has been documented previously, our findings suggest that mucosal priming with live virus is necessary to obtain an IgA response after IPV booster vaccination.