Nature of macrophage-T cell interaction in secondary helper cell generation in vitro. Genetic restriction of macrophage-T cell interaction, which determines T-B genetic restriction

Induction of helper T cells by antigen specific factor from macrophages

An immunostimulatory antigen specific factor (ASF) was found to be secreted by antigen-pulsed macrophages. Macrophages obtained from peritoneal exudate of C57BL/6 mice were pulsed with horse spleen ferritin (HSF). The PM10 ultrafiltration membrane-retained supernatant from the cultures of these macrophages was able to generate helper T cells when introduced into cultures of nylon wool purified T lymphocytes from spleens of C57BL/6 mice. The generation of helper T cells was measured by the cooperation between ASF-induced T cells and splenic B cells in the presence of trinitrophenyl (TNP)-HSF, and subsequently by the anti-TNP plaque forming cell (PFC) assay using TNP-coated sheep red blood cells. The number of PFC obtained from these cultures was significantly higher than the control (T cell cultures without ASF). Background levels of PFC were obtained when the T-B cooperation cultures were challenged with other haptenated antigens (e.g. TNP-BSA) instead of TNP-HSF. In addition, ASF from allogeneic macrophages was unable to facilitate helper cell induction. These results indicated that helper T cell induction by ASF is antigen specific as well as genetically restricted. When small amounts of ASF were injected into syngeneic mice without any adjuvant, specific helper T cells could be obtained from the spleens of these animals which showed that ASF is also active in vivo.

Role of lymphokines in the immune response of the inner ear

In secondary inner ear responses against keyhole limpet hemocyanin (KLH), the characterization of interleukin-2 levels in perilymph and serum developing over 5 days in Hartley guinea pigs was investigated using an immunoassay. No interleukin-2 levels were detectable at Day 0 in serum and perilymph. The earliest perilymph IL-2 levels were observed after 6 h, peaking at 18 h and decreasing to zero by Day 5. In contrast, during this observation period, no IL-2 was detectable in serum or perilymph from control ears. Since previous work has identified T-helper cells in the endolymphatic sac, this site appears to be the probable source of interleukins. This study provides further support for the existence of an inner ear immune response which is regulated by lymphokines. Furthermore, interleukins may be a chemoattractant for cells entering the cochlea during the immune response.

Evaluation of accessory cell heterogeneity. I. Differential accessory cell requirement for T helper cell activation and for T-B cooperation

Several Ia+ tumor cell lines and peritoneal exudate macrophages were tested as accessory cells (AC) for the activation of antigen-specific T cells and for T-B cooperation. The macrophages and all the Ia+ tumor lines tested induced the release of lymphokines from T cells in a major histocompatibility complex (MHC)-restricted fashion and reconstituted the antibody responses of AC-depleted spleen cells or of purified T and B cells. However, only the normal macrophages but none of the tumor lines induced carrier-specific T helper (Th) cells which help B cells for specific antihapten antibody responses by linked recognition. For T-B cooperation accessory cells were also required, but in contrast to Th cell activation any type of Ia+ AC (e.g. macrophage or tumor line) was effective. Strong MHC-restriction between the lymphocytes and the AC was seen if antigen-pulsed AC were added into the AC-depleted T-B cooperation cultures. If the AC and antigen were concomitantly added to the AC-depleted T-B cultures, MHC-restriction was less obvious. Concanavalin A supernatant reconstituted the response of AC-depleted T-B cultures provided antigen-specific Th cells and the hapten-carrier conjugate were present. If, however, tumor line-activated T cells were added instead of macrophage-induced Th cells, no cooperation with B cells took place even in the presence of Con A supernatant. The results obtained demonstrate a differential AC requirement for the induction of Th cells depending on the differentiation stage of the Th cells.

The Ia-1 gene effects T-B cell collaboration for the in vitro antibody response

The I-A subregion mutant B6.C-H-2bm12 (bm12) and the C57BL/6 parent were used to examine the role of the Ia-1 gene product as a restriction element in the antibody response to sheep red blood cells (SRBC). Using an in vitro culture system, it was shown that cooperation between histocompatible T cells, B cells and macrophages was required to generate a secondary IgM response to SRBC. The alteration in the Ia-1 gene in bm12 altered the ability of bm12 T cells to collaborate with C57BL/6 B cells, but not with C57BL/6 macrophages. Similarly, C57BL/6 T cells could not collaborate with bm12 B cells. The mutation in bm 12 did not affect the ability of T cells to interact with C57Bl/6 macrophages, either in vitro or in vivo, or of bm12 macrophages to interact with C57BL/6T cells. Thus in this system, the Ia-1 gene product restricts T-B cell interaction but not T cell-macrophage interaction.

Accessory cell-dependent selection of specific T-cell functions

Activation of many T-cell functions depends on their interaction with antigen-presenting accessory cells which express I region associated (Ia) products. Cells expressing accessory cell function include those of the monocyte/macrophage lineage and dendritic cells. More recently, B cells and a number of tumour cell lines of macrophage or B-cell origin were shown to act as accessory cells in certain assays. We showed previously that normal peritoneal exudate macrophages (PEC) induced both T-cell proliferation as well as T-cell help, whereas various Ia+ tumour lines of macrophage or B-cell origin, although stimulating antigen-specific T-cell proliferation, did not significantly activate T-cell help. We report here that during the initial T-cell activation in vitro accessory cells (PEC or Ia+ tumour cells) select particular T cells to express previously determined functions. Moreover, some tumour cell lines induce suppressor T cells which inhibit helper activity.

Cellular interactions involved in T-dependent B-cell activation

in this article, Michael Julius provides a framework within which to consider the activation requirements of B cells limited by T-helper cell activation and recognitive properties associated with effeclor function, focusing mainly on the requirement for an MHC-restricted T-B interaction.

Dissociation of two signals required for activation of resting B cells

Cellular interactions involved in the T cell-dependent activation of B cells were analyzed by using lines and clones of helper T cells specific for determinants expressed on the B cell surface. Activation of male antigen-, M locus-, and H-2-specific T cells was shown to support polyclonal Ig production by a population of B cells that did not require T-cell-B-cell interaction for induction/amplification. However, these T cells alone did not activate gradient-purified small (resting) B cells. The activation of small B cells was shown to require not only a signal derived through an antigen-specific T-helper cell-B cell interaction but in addition a second signal that could be provided by anti-Ig antibodies.