Transfer of memory cells into antigen-pretreated hosts. I. Functional detection of migration sites for antigen-specific B cells

Recall of B cell memory depends on relative locations of prime and boost immunization

Immunization or microbial infection can establish long-term B cell memory not only systemically but also locally. Evidence has suggested that local B cell memory contributes to early local plasmacytic responses after secondary challenge. However, it is unclear whether locality of immunization plays any role in memory B cell participation in recall germinal centers (GCs), which is essential for updating their B cell antigen receptors (BCRs). Using single B cell culture and fate mapping, we have characterized BCR repertoires in recall GCs after boost immunizations at sites local or distal to the priming. Local boosts with homologous antigen recruit the progeny of primary GC B cells to recall GCs more efficiently than do distal boosts. Recall GCs elicited by local boosts contain significantly more B cells with elevated levels of immunoglobulin (Ig) mutation and higher avidity BCRs. This local preference is unaffected by blocking CD40:CD154 interaction to terminate active, GC responses. Local boosts with heterologous antigens elicit secondary GCs with B cell populations enriched for cross-reactivity to the prime and boost antigens; in contrast, cross-reactive GC B cells are rare after distal boosts. Our results suggest that local B cell memory is retained in the form of memory B cells, GC B cells, and GC phenotype B cells that are independent of organized GC structures and that these persistent "primed B cells" contribute to recall GC responses at local sites. Our findings indicate the importance of locality in humoral immunity and inform serial vaccination strategies for evolving viruses.

The role of germinal centres in the generation of immunological memory

Germinal centres are areas of B lymphocytes proliferation that appear in primary lymphoid follicles after immunization. The results summarized here implicate these structures in the establishment of immunological memory for antibody production. It appears that after primary immunization antigen-antibody-complement complexes become trapped on the membrane of specialized dendritic cells in lymphoid follicles, and these complexes provide the stimulus for germinal centre formation. In support of this, immunization with preformed antigen-antibody complexes, rather than with antigen, leads to the earlier appearance of germinal centres and memory cells, and also accelerates the selective triggering of precursors capable of producing high affinity antibodies.

Role of different lymphoid tissues in the initiation and maintenance of DNA-raised antibody responses to the influenza virus H1 glycoprotein

Antibody responses in mice immunized by a single gene gun inoculation of plasmid expressing the influenza virus H1 hemagglutinin and in mice immunized by a sublethal H1 influenza virus infection have been compared. Both immunizations raised long-lived serum responses that were associated with the localization of antibody-secreting cells (ASC) to the bone marrow. However, the kinetics of these responses were 4 to 8 weeks slower in the DNA-immunized than in the infection-primed mice. Following a gene gun booster, the presence of ASC in the inguinal lymph nodes, but not in other lymph nodes, revealed gene gun responses being initiated in the nodes that drain the skin target site. Both pre- and postchallenge, the DNA-immunized mice had 5- to 10-times-lower levels of antibody and ASC than the infection-primed mice.

Pulmonary immune memory: localized production of antibody in the lung after antigen challenge

In comparison to primary immune responses after lung immunization, the level of antigen-specific antibody and the number of cells producing specific antibody are significantly increased after challenging the lungs with antigen. The response of immune memory cells in the lung to an antigen challenge could be responsible for this elevated immune response. However, increased numbers of antibody-producing cells, possibly produced in the lung-associated lymph nodes, are also found in the blood after an antigen challenge. Therefore, it is possible that both the response of immune memory cells in the lung, and the recruitment of antibody-producing cells from the blood, contribute to the elevated levels of antibody in the lung after an antigen challenge. This study compared the level of antibody produced in the lung by the response of pulmonary immune memory cells with the level of antibody produced by antibody-forming cells that enter the lung from blood after an antigen challenge. This comparison was made possible by immunizing and challenging two lung lobes of dogs with two antigens. The immune responses to both antigens were then evaluated in both lung lobes after primary immunization and challenge. Data from these evaluations showed that most antibody in the lung after an antigen challenge is produced by a localized anamnestic response of pulmonary immune memory cells. A significantly lower level of antibody entered the lung from the vasculature and/or was produced by antibody-forming cells that entered the lung from blood after an antigen challenge.

Differential enhancement and distribution of antigen-specific cells in various lymph nodes in response to locally inoculated bacterial antigens

The proliferation responses of antigen-specific lymphocytes from various anatomical sites were studied in dairy goats locally immunized with heat-killed Staphylococcus aureus (HKS). Animals were inoculated three times subcutaneously in the right udder with HKS at 1 month intervals. One week following the last inoculation, prescapular, mesenteric and ipsilateral (draining) and contralateral (non-draining) suprammammary lymph nodes were collected and the cells assayed in 3- and 6-day cultures to determine the immune proliferative responses of antigen-specific lymphocytes to HKS and the polyclonal T cell mitogen phytohemagglutinin (PHA). The cells from draining and non-draining supramammary lymph nodes responded to HKS in 3-day cultures. Peripheral lymph nodes, such as the prescapular, showed similar responses. In contrast, mesenteric lymph nodes responded optimally in 6-day cultures, notably to lower concentrations of the antigen. Cells from all lymph nodes tested showed increased responses to PHA in immunized animals, although non-draining lymph nodes demonstrated a greater response to the T cell mitogen than those of draining lymph nodes. These results suggest that unilateral introduction of Staphylococcus cell antigens to the supramammary region can induce an anamnestic response in ipsilateral as well as contralateral supramammary lymph nodes and other distant peripheral lymphoid organs. Furthermore, these data indicate that cells from intestinal lymph nodes respond differently from those of peripheral lymph nodes, suggesting the presence of a unique gastrointestinal lymphoid cell circulation in goats. Concomitant peripheral responses may be attributed to memory cell migration or to antigen leakage and relocation to distant sites from the inoculated region. Analysis with PHA suggests a difference in general responsiveness and perhaps, immunocompetence, by lymphocyte populations in various lymphoid tissues of immunized animals.

Lymph node involvement in a humoral immune response

Mice were primed subcutaneously in the hind footpads with horseradish peroxidase (HRP) and boosted intravenously 10 weeks later. The appearance of cells with cytoplasmic anti-HRP antibody was studied in several lymph nodes. It appeared that following intravenous boosting antibody-forming cells appeared in significant numbers in the popliteal, the lumbar, and (in some animals) the sciatic lymph nodes exclusively. In the other lymph nodes examined specific antibody-forming cells were observed only occasionally. By subcutaneous injection of Evans blue in the hind footpads it was shown that the subcutis of the hind footpads of these animals is drained by the popliteal lymph nodes, the lumbar lymph nodes, and (to a lesser degree) the sciatic lymph nodes. The presence of trapped immune complexes within lymph node germinal centers was confined to these three nodes. Based on these findings, it is concluded that specific antibody-forming cells during the secondary response in these mice are induced exclusively in the lymph nodes draining the site of primary immunization.

Physiology of Igd. II. Lack of humoral immune responsiveness in lymph nodes of mice treated with anti-IgD from birth

Previous studies have shown that anti-IgD-suppressed mice give normal primary and secondary splenic plaque-forming cell responses following i.v. challenge, although mice suppressed by the injection of anti-IgD from birth lack IgD-bearing cells in all lymphoid tissue examined. The present studies show that, in contrast, secondary immune responses in regional lymph nodes of such mice, even after i.v. priming with trinitrophenylated B. abortus, respond to a challenge injection in the footpad up to only less than 10% of control levels. When compared with respect to B cell numbers transferred, primed spleen cells from control and anti-IgD-suppressed mice are about equally effective in producing adoptive secondary plaque-forming cell responses in the spleens of recipient mice. Lymph nodes in recipients of anti-IgD-suppressed primed spleen cells show much lower responses than do lymph nodes in recipients of control primed cells, both upon immediate and delayed challenge with antigen in the footpads. It is concluded that the immunodeficiency caused by suppression with anti-IgD is much more marked in peripheral lymph nodes than in the spleen. The possible relationship of these results to the migratory properties of IgD+ as compared to IgD-B cells is discussed.

Transfer of memory cells into antigen-pretreated hosts. II. Influence of localized antigen on the migration of specific memory B cells

Following i.v. injection, 2,4,6-trinitrophenol (TNP)-primed memory cells localized in recipient lymph nodes draining a footpad injection of TNP-hemocyanin (TNP-KLH) in greater numbers than in contralateral nodes draining a p-azobenzenearsonate-coupled KLH injection. Such hapten-specific, unilateral memory B cell localization was still observed in immunosuppressed mice when antigen injections were given as long as 4 days prior to the memory cell transfer. The memory cells could be challenged to form plaque-forming cells by footpad injections of TNP-labeled Brucella abortus at 5 days, but not one day, after cell transfer. The present studies further clarify some parameters of this adoptive memory, as a model for the study of persistent local memory. Measures that promoted the unilateral lymph node retention of 125I-labeled antigen also facilitated unilateral accumulation of TNP-specific memory cells. Such measures included pretreatment of the recipients with cyclophosphamide, rather than gamma irradiation, injection of anti-carrier antibody the day before antigen, or use of small doses of preformed immune complexes instead of antigen alone. In general, a high ratio of lymph node-to-spleen and lymph node-to-blood concentration of antigen in recipients appeared crucial for unilateral localization of memory B cells. Splenectomy of recipients prior to cell transfer enhanced the difference in plaque-forming cell responses between draining and contralateral nodes, but decreased their difference when performed 1 day after cell transfer, suggesting that the spleen may have served as a trap for memory cells. I.v. injection of antigen at the time of B cell transfer also interfered with unilateral localization. The results demonstrate that in the presence of persisting depots of antigen within lymph nodes (and absence of significant amounts of antigen elsewhere), memory B cells can be retained locally without activation into antibody-secreting cells. This mechanism may, therefore, by responsible for the phenomenon of local, humoral, immunological memory.

Specific selection of antigen-reactive lymphocytes into antigenically stimulated lymph nodes in sheep

Sheep were primed to a variety of antigens and the efferent lymphatic from a popliteal lymph node was cannulated. The cannulated node was challenged repeatedly with PPD and all the lymph and cells removed from the animal. During this time the PBL were monitored for reactivity to all antigens (purified protein derivative of tuberculin [PPD], johnin, and keyhole limpet hemocyanin [KLH]) by the vitro transformation assay. The response of these cells to PPD was found to be gradually eliminated after repeated challenge of the cannulated node with that antigen. The response to the other antigens was unimpaired. No depletion of this response to PPD occurred in cannulated sheep when the antigen was given into a noncannulated node. In vivo delayed-type hypersensitivity skin test and helper T cell assays confirmed that there is a specific selection of antigen-reactive cells from the recirculating lymphocyte pool into antigen-stimulated lymph nodes.