Rapid changes in the regulatory potential of autologous anti-idiotopic T cells during an antigen-driven primary response

The antibody response of C57BL/6 strain mice to Streptococcus pneumoniae R36a (Pn) is dominated by the T15 idiotype, but the responding cells appear to be idiotypically heterogeneous, in that individual antibody plaque-forming cells (PFC) may express some but not all idiotopes (Id) of the T15 complex. The presence of these distinct Id on the PFC was detected by a plaque-inhibition assay with three different monoclonal anti-Id antibodies, designated AB1-2, MaId5-4, and B36-82. A periodic change in the expression of AB1-2 and MaId5-4 Id was observed during primary (IgM) antibody response to Pn in the spleen. Those two Id were poorly expressed in the log phase of the response between day 2 and day 4 after immunization (few PFC in the spleen bore the Id), but they became detectable on the majority of PFC at the peak of the response, day 5 to day 7. The proportion of the Id-(AB1-2 or MaId5-4) positive PFC declined, again at day 10 after immunization. In contrast, the B36-82 Id was expressed on greater than or equal to 80% PFC throughout the entire primary response. The possibility that the apparent changes in the Pn-reactive cell populations are regulated by autologous anti-Id T cells was tested in vitro. Normal, unimmunized B cells were cultured with Pn, either alone or in the presence of syngeneic T cells isolated from the spleen of mice at the appropriate intervals after immunization: day 2 (T2), day 5 (T5), and days 10 to 14 (T10 to T14); T cells from unimmunized donors (T0) served as a control. The specific response after 4 days in culture was determined in regard to the total PFC as well as the proportion of PFC expressing the Id. Pn-stimulated B cells, alone or with the control T0 cells, produced moderate, variable levels of AB1-2+ and MaId5-4+ PFC. The expression of these two Id in the assay cultures was suppressed by addition of either T2 cells or T10-14 cells, but it was enhanced if T5 cells were added. However, these various T cell populations did not differ in their effect on the total PFC response. Also, the proportion of PFC bearing the third Id, B36-82 was high, and it was not consistently influenced by the added T cells.(ABSTRACT TRUNCATED AT 400 WORDS)     

Regulation of idiotope expression. III. H-2 influences the magnitude and the idiotypy of a T-independent antibody response in mice of certain genetic backgrounds

Antibody response to the phosphocholine (PC) epitope on Streptococcus pneumoniae R36a (Pn), a T-independent Ag type 2, was studied in H-2 congenic mouse strains. The PC-specific antibody plaque-forming cells (PFC) were enumerated in the spleen at various intervals after the primary Pn injection, and the proportion of PFC that produced antibody expressing the AB1-2 idiotope (Id) was determined by using the corresponding monoclonal anti-Id. AB1-2 is a cross-reactive Id, detectable on germline-encoded PC antibody of the T15 family, and on most, but not all, somatic variants of that antibody. The specific PFC responses in BALB/c (H-2d) and BALB.B (H-2b) strains were of comparable magnitude and most, if not all, PFC were ABl-1 Id-positive (AB1-2+). This was not the case in the responses of the B10D2 (H-2d) vs C57BL/10 (H-2b) strains and the D1.C (H-2d) vs D1.LP (H-2b) strains (on DBA/1 background). In each of these pairs, the H-2d mice were high responders, and the response was dominated by AB1-2 Id (greater than or equal to 80% AB1-2+ PFC at the peak, on day 5). The H-2b mice were low responders, and only a minor proportion of PFC (less than or equal to 30%) were AB1-2+; an increase of AB1-2+ was seen later in the response (d.10). The results of PFC assays were confirmed by measuring the PC-binding antibody and AB1-2 Id in the sera of D1.C and D1.LP mice immunized repeatedly with Pn. Moreover, D1.LP mice that had very low levels of AB1-2 Id had higher serum levels of antibody expressing two other T15 Id, B36-82, and B24-44. The B36-82 and B24-44 Id have been previously found on somatic variants of PC antibody expressed independently of the Ab1-2 Id. The concentrations of these two Id in D1.LP mice after repeated immunization approached those in D1.C. These results indicate that 1) the H-2 allelism may have a significant effect on TID antibody response in mice of a certain genetic background, but not in the BALB/c; and 2) the idiotypic repertoire of the response may be influenced by H-2 at the level of clonal variants of PC-reactive cells.     

The repertoire diversity and magnitude of antibody responses to bacterial antigens in aged mice: I. Age-associated changes in antibody responses differ according to the mouse strain

Aging influences the host immune responses in various ways. In aging mice we have studied the antibody responses to two unrelated bacterial antigens. Streptococcus pneumoniae R36a vaccine (Pn) and TNP coupled to Brucella abortus (TNP-BA). Aged animals (20-24 months old) of the C57BL/6 strain had markedly reduced numbers of IgM antibody plaque-forming cells (PFC) to Pn as compared to young/adult mice (2-3 months old). In contrast, the anti-Pn IgM PFC responses of aged BALB/c mice were consistently higher than they were in the young/adult mice. The increased anti-Pn responses were not due to a nonspecific immunostimulation, because the responses of aged BALB/c mice to TNP-BA were lower as compared to the adults. However, the aged BALB/c mice responded relatively poorly to Pn challenge, and their IgG responses (as determined by ELISA plaque assay) demonstrated a very high individual variability. The clonotypic diversity of anti-Pn response in young BALB/c and C57BL/6 is limited, such that the majority of PFC produce antibody that express all idiotopes (Id) of the T15 immunoglobulin encoded in the VH-S107/Vk22 genes. In contrast, the PFC from aged mice are diverse, expressing incomplete T15 Id or none at all, suggesting that the antibodies are encoded by altered T15 genes and by different, non-T15 genes. Our data demonstrate that the age-related changes in the magnitude of antibody response to certain antigens are influenced by the host genetic make-up, and that the changes in magnitude and diversity of antibody response may be unrelated to each other.     

Regulation of idiotope expression. IV. Genetic linkage of two D region-dependent T15 idiotopes to the IgH allotype

The idiotopic (Id) repertoire of antibody response to phosphocholine was studied in mouse strains with different IgH allotypes. The T15 idiotype-bearing (T15+) serum antibody and antibody plaque-forming cells (PFC) were characterized with four monoclonal anti-Id that recognize distinct Id determinants on T15+ antibody encoded by VH-1 (of the S107 gene family), DH FL16.1, JH-1 and Vk22 germ-line genes. We have previously shown that expression of the Id designated AB1-2 and B36-82 depends on the third hypervariable loop (D region), whereas the other Id, MaId5-4 and B24-44, are influenced by VH structures outside of the D region. All four Id were expressed in the PC-response of all mouse strains tested, except the Ighj strains (C3H/HeJ, CBA/H-T6, PL/j), where the D region-dependent Id, AB1-2 and B36-82, were absent. The other Id, however, were normally expressed on individual PFC as well as the serum antibody of the Ighj strains. Expression of AB1-2 and B36-82 on 50% of PFC occurred in (BALB/c-Igha x C3H/HeJ-Ighj)F1 mice. The absence of Id correlated with a unique RFLP of the S107 gene family in Ighj strains. Finally, Id expression segregated with the appropriate RFLP pattern in individual (BALB/c x C3H/HeJ)F2 mice. These data demonstrate a selective genetic linkage of discrete T15 Id determinants, AB1-2 and B36-82 with the Igh allotype. By comparing these results with the available Ig sequences, we suggest that the Ighj allotype may be associated with an allelic form of the DH-FL16.1 segment which with VH-1, JH-1, and the Vk 22 code for the phosphocholine-specific antibody in the mouse.     

Induction of antigen-specific antibody responses in primed and unprimed B cells. Functional heterogeneity among Th1 and Th2 T cell clones

CD4+ T cells have been recently divided into two subsets. The functions of these subsets are thought to be distinct: one subset (Th1) is responsible for delayed type hypersensitivity responses and another (Th2) is primarily responsible for induction of antibody synthesis. To more precisely define the roles of both subsets in humoral immune responses, we examined the ability of a panel of nominal antigen specific Th1 and Th2 clones to induce anti-TNP specific antibody synthesis in TNP-primed or unprimed B cells. Four of nine Th1 clones induced little or no antibody synthesis with TNP-primed B cells. However, five other Th1 clones were very effective at inducing IgG anti-TNP plaque-forming cell (PFC) responses in primed B cells. One of these Th1 clones was analysed in detail and found to also provide helper function for unprimed B cells. Cognate B-T cell interaction was required for induction of both primary and secondary responses with this clone, indicating that a Th1 clone could function as a "classical" Th cell. The seven IL-4 producing Th2 clones examined were also heterogeneous in their ability to induce antibody secretion by TNP-primed B cells. Although four of the Th2 clones induced IgG and IgM anti-TNP PFC responses, two Th2 clones induced only IgM and no IgG antibody, and another clone failed to induce any anti-TNP PFC. All Th2 clones failed to induce any anti-TNP PFC. All Th2 clones produced high levels of IL-4, but "helper" Th2 clones produced significantly greater amounts of IL-5 than "non-helper" Th2 clones. These studies indicate that some IL-2- and some IL-4-producing T cell clones can induce TNP-specific antibody in cell clones can induce TNP-specific antibody in primed and unprimed B cells, and that Th1 and Th2 clones are heterogeneous in their ability to induce Ig synthesis. Therefore, although T cell clones can be classified as Th1 or Th2 types according to patterns of IL-2, IFN-gamma, or IL-4 synthesis, the functional capacity to induce antibody synthesis cannot be predicted solely by their ability to secrete these lymphokines.     

T cell responses to select Ia determinants using the I-A mutant mouse strain B6.C-H-2bm12

The T cell repertoire of B6.C-H-2bm12 mice (an I-A mutant mouse strain) to wild-type Iab antigens was investigated using both secondary proliferative cultures and cloned T cell lines. Because bm12 mice have a gain-loss mutation of their gene encoding the Ia beta-chain polypeptide, bm12 anti-B6 T cell responses are specific for the select component of Iab specificities that was lost as a result of the mutation. Although stimulator cells bearing Iab antigens elicited the strongest responses, Iaq, d, and s antigens also resulted in reproducible stimulations of these bm12 anti-B6-primed T cells. Cloned T cell lines isolated from bm12 anti-b6 cultures revealed similar findings, with most clones recognizing determinants unique for Iab antigens; however, clones showing cross-reactions with Iad and/or q were also selected. Using F1 hybrid responder T cells (mutant x cross-reactive strain), we further dissected this cross-reactivity into several distinct cross-reactive determinants. Because bm12 mice lack the serologically defined Ia differentiation antigen W39, T cell recognition of this determinant was investigated by using bm12 anti-B6-primed cells. Stimulation by Ia.W39+ cells was appreciably better than by Ia.W39- (Xid-defective) cells, suggesting that bm12 T cells recognize an Xid-regulated, W39-like Ia differentiation antigen.     

Idiotypic properties of the murine anti-arsonate antibody response: B- and T-cell influences

In a previous report characterizing the arsonate (ABA)-specific plaque-forming cell (PFC) responses of A/J mice induced by ABA-KLH, two interesting characteristics of the idiotypic (Id) profile were noted: (1) an apparent Id selectivity in the isotype switch since the earliest appearing IgG PFC in the primary response were significantly more "cross-reactive Id" (CRI)-dominant than the IgM PFC population, and, (2) a temporal waning of CRI dominance with time among IgG PFC, from 75-100% CRI+ PFC to about 25-45% CRI+ PFC in secondary responses. Experiments were performed to determine whether these effects are largely attributable to T or to B cells. Mice were immunized with a T-independent (TI) form of ABA (ABA-Brucella abortus) and apparent Id selectivity was observed; the earliest IgG PFC averaged 75% CRI+ while IgM PFC were only 39% CRI+. Due to the TI nature of the Ag, this provides suggestive, but not conclusive, evidence that the Id asymmetry in the isotype switch may be attributable to the direct interaction of Ag with B cells. Other studies addressed the temporal shift in CRI dominance. First, it was found that preexposure of mice to either KLH or to ABA (on an irrelevant carrier) resulted in diminished CRI dominance in subsequent "primary" responses to ABA-KLH. Secondly, adoptive transfer experiments with B and T cells from virgin mice (Bv, Tv) or ABA-KLH-primed mice (Bp, Tp) showed that recipients of Bv + Tp or Bp + Tv generated anti-ABA PFC responses with intermediate CRI levels. The Tv cells had some preferential tendency to activate CRI+ clones in the Bp population. The results demonstrate that CRI levels are jointly determined by the immune status of both B and T cells. A simple model is offered which accounts for early Id dominance and its gradual decline and has as its central postulate the assumption that CRI+ B cells in the virgin ABA-specific repertoire have an affinity advantage over CRI- clones.     

"Nonspecific" immunoenhancing T cells in tumor-bearing mice include anti-idiotypic subsets

Splenocytes from DBA/2 mice inoculated 3 wk earlier with syngeneic P815 mastocytoma tumor cells produce increased numbers of antibody plaque-forming cells (PFC) when stimulated with either sheep red blood cells (SRBC) or phosphorylcholine (PC) on Streptococcus pneumoniae R36a in vitro. The nature of this nonspecific hyperreactivity was investigated in mixed cultures of purified splenic T and B cells. The addition of T cells from P815 tumor-bearing mice (TP815) into the cultures of normal B cells produced a significant enhancement of the PFC response to both SRBC and PC, when compared with the effect of normal T cells added to control cultures. The idiotypic profile of the enhanced anti-PC response was studied by a PFC-inhibition assay with monoclonal antibodies against two distinct idiotopic determinants (Id) of the T15 family. Normal B cells produced greater than 90% of T15 Id-positive (Id+) PFC. Addition of normal T cells diminished the proportion of T15 Id+ PFC to approximately 60%, whereas the rest of PFC were Id-. Addition of the immunoenhancing TP815 cells into the normal B cells cultures elevated the number of both T15 Id+ and Id- PFC responses, proportionally. However, when TP815 cells were first incubated on T15 protein-coated dishes and the non-adherent fraction was added to B cell cultures, the anti-PC PFC response remained enhanced but consisted of predominently T15 Id- PFC. These observations suggest that the early stage of P815 tumor growth activates various populations of specific helper/amplifier T cells including subsets with anti-idiotypic activity and that the generalized increase of antibody response to various antigens in tumor-bearing mice may be regarded as a polyclonal activation of specific T cells.     

TRF requirements for in vitro PFC responses to SRBC and R36a. I. TRF is distinct from IL 2 but indistinguishable from polyclonal BCSF

In vitro PFC responses to the thymus-independent (TI) antigen Streptococcus pneumoniae R36a require T cell replacing factor(s) (TRF). This requirement for TRF is as significant as for the thymus-dependent (TD) antigen SRBC. TRF is shown to be distinct from IL 2 by the following observations: 1) culture supernatants from the cloned T cell line L2, collected over an 8-day period after allogeneic stimulation, transiently contain IL 2 activity but maintain high levels of TRF activity throughout 192 hr; 2) L2V, a variant subclone of L2, produces much higher levels of TRF activity than the parental line but no detectable IL 2 activity; 3) the addition of IL2+, TRF- supernatants from the T cell hybridoma FS6-14.13 does not affect the L2V SF-driven PFC responses to R36a or SRBC; and 4) the addition of contaminating T cells to cultures containing T cell-depleted spleen cells, L2V SF, and antigen does not affect the PFC response. TRF does appear to be indistinguishable from polyclonal B cell stimulating factor (BCSF), which stimulates polyclonal PFC responses in the absence of antigen, mitogen, or anti-Ig. The TRF and BCSF activities of L2V SF could not be separated by ion-exchange, hydrophobic-interaction, and gel-filtration chromatography. TRF and BCSF have an apparent m.w. of approximately 40,000.     

Factors determining the effects of chronic protein-deficiency on antibody responses to sheep red blood cells and Brucella abortus vaccine in mice.

Chronic protein-deficiency in weanling mice caused variable suppression of the humoral plaque-forming cell (PFC) responses to sheep erythrocytes. This was most prominent at high antigen doses and did not increase when mice were maintained on the diets for longer periods. Antibody responses produced by deficient mice were often short-lived and involved high levels of IgM. Total PFC counts were depressed slightly more than were circulating antibodies. Antibody responses to Brucella abortus were slightly decreased by protein-deficiency at high antigen doses but were normal or elevated at lower doses, the proportion of IgM produced was increased and the splenomegaly response to B. abortus was severely depressed. These results suggest that the depression of antibody production by protein-deficiency is not simply due to an impairment of helper T cell function, but a reduction in the availability or effectiveness of macrophage and regulatory or suppressor T cells may be important.     

Collaboration of Th1 and Th2 T cell clones in specific antibody responses: regulation of the IgM response to phosphorylcholine

Carrier (KLH)-specific type 1 T cell clones (Th1), which are defined by secretion of IL-2 and IFN-gamma but not IL-4, and type 2 (Th2) clones, which secrete IL-4, but not IL-2 or IFN-gamma, have been isolated and analyzed for their ability to collaborate in providing help for B cells to secrete phosphorylcholine-specific IgM antibodies. The resulting antibody responses exhibited a characteristic pattern suggesting two distinct regulatory interactions among the Th1, Th2, and B cells. At low doses of antigen, Th1 cells enhanced the helper function of the Th2 cells, an effect due primarily to IL-2. At high doses of antigen, Th1 cells or IFN-gamma inhibited Th2-dependent antibody responses. The inhibitory effect of Th1 or IFN-gamma affected primarily the hapten-carrier-linked portion of the response. The overall effect was a modulation of the antigen dose-response curve for antibody production, eliminating the sharp increases in dose response mediated by isolated T cell clones. The data suggest that collaborative interactions of Th1 and Th2 cells in antibody production may have important physiological consequences.     

Hapten-specific T cell response to azobenzenearsonate-N-acetyl-L-tyrosine in the Lewis rat. II. Induction of helper activity demonstrated by TNP-haptenated ABA-peptide-Ficoll

In an effort to study T cell functions in Lewis rats immunized with ABA-N-acetyl-L-tyrosine (ABA-tyr), we developed an antigen that provides a sensitive assay of ABA-specific helper function that is read as an increase in TNP-specific plaque-forming cells (PFC). This antigen has ABA coupled to AECM-Ficoll by virtue of a tripeptide (tyr-ala-ala) spacer and TNP coupled to the AECM side chains. At subimmunogenic doses, this antigen induced 400 anti-TNP PFC/10(6) spleen cells in ABA-tyr-immunized rats. As many as 8000 PFC/10(6) spleen cells were induced with larger doses of antigen (200 micrograms). By contrast, only 490 PFC/10(6) spleen cells could be induced with 1 mg of the conventional doubly haptenated protein carriers such as ABA-BSA-TNP. Both direct and indirect PFC were induced by this antigen in primed rats. The use of this antigen and passive transfer techniques to study ABA-specific helper activity revealed some differences from ABA-specific delayed-type hypersensitivity (DTH) and in vitro proliferation, which were studied previously. Cells responsible for helper activity appeared sooner after immunization and were found most prominently in peritoneal exudates but also significantly in spleen where the cells responsible for DTH or in vitro proliferative responses were never found. By contrast, helper cells were not seen in lymph nodes, where some proliferative activity could be found. Of these three ABA-specific T cell functions, helper activity was least easily suppressed by the previously used regimens of ABA-tyr in incomplete freunds adjuvant (IFA). Moreover, helper activity appears after injection of ABA-tyr in IFA, a method that has never in our hands yielded detectable DTH or in vitro proliferative responses. Despite these differences, phenotyping with monoclonal antibodies indicated that cells responsible for helper and proliferative activities were both W3/25+ and OX8-.     

Regulation of T15 idiotype dominance. III. Phosphocholine-specific B-cell activation in vivo requires major histocompatibility complex-restricted T-cell help

We have examined the requirement for major histocompatibility complex (MHC)-restricted T-cell help in the secondary in vivo antibody response to phosphocholine (PC). The memory response to PC has been demonstrated previously to be comprised of T15-dominant IgM and IgG3 plaque-forming cells (PFC) derived primarily from the Lyb-5+ B-cell subset, and IgG1 and IgG2 PFC, few of which bear the T15 idiotype and are predominantly derived from the Lyb-5- B-cell subset. Using carrier-primed (A X B)F1 T cells which have matured in a parentA chimeric environment so that "self" recognition is of the MHC determinants of parentA but not parentB, we have found that parentA PC-primed B cells, but not parentB PC-primed B cells, are activated. Even in the presence of an ongoing parentA anti-PC response, parentB PC-primed B cells were not activated, indicating that the restriction was between the helper T cell and the B cell, not between T-helper and accessory cells. MHC-restricted T-cell help was required by B cells producing T15+ and T15- IgM, IgG3, IgG1, and IgG2 responses.     

Immunoregulation in the rat: cellular and molecular requirements for B cell responses to types 1, 2, and T-dependent antigens

The requirements for primary in vitro plaque-forming cell (PFC) development in cultures of purified rat splenic B cells have been examined. Rat B cells were directly responsive to the type 1 antigen trinitrophenyl-Brucella abortus (TNP-BA), but both T cells and adherent accessory cells were required for B cell responses to the type 2 antigen TNP-Ficoll and the T cell-dependent (TD) antigen sheep erythrocytes (SRBC). However, the cellfree supernatants from concanavalin A-induced spleen cells of rat or mouse origin replaced the requirement for T cells and macrophages, and resulted in PFC development in response to TNP-Ficoll and SRBC and augmented PFC numbers in response to TNP-BA. Culture supernatants from induced murine T cell and macrophage cell lines were used to partially deduce the molecular requirements for the support of PFC development by rat B cells to these three antigens. Supernatants from the EL-4 (EL-4 sup) and B151 K12 (B15 sup) T cell lines augmented TNP-BA responses, suggesting that B cell growth factor II (BCGF-II) mediated this effect. An admixture of purified interleukin 2 (IL 2) and B15 sup supported PFC development to SRBC; indicating that IL 2, BCGF-II, and the T cell-replacing factor in B15 sup (B15-TRF) were sufficient to support this response. In addition, the IL 2 plus B15 sup-supported anti-SRBC PFC response was increased by the addition of an interleukin 1-containing fraction from the supernatant of the macrophage line P388D1. PFC development in response to TNP-Ficoll had the most stringent requirements and only occurred in the presence of EL-4 sup and B15 sup (IL 2, BCGF-I, BCGF-II, EL-TRF, B15-TRF). These data indicate that different cellular and molecular requirements exist for PFC development in response to types 1, 2, and TD antigens by rat B cells.     

Expression of T cell receptor-alpha and -beta subunits in human thymocytes. An immunocytologic study

The expression of the T cell receptor (Ti)-alpha and -beta subunits in human thymocytes was studied with the use of two rabbit antisera directed at constant regions of human Ti-alpha- and Ti-beta-chains (H36 and H38, respectively). Immunoperoxidase techniques were employed to count by light and electron microscopy the cells, in the various thymocyte subsets, bearing Ti-alpha and Ti-beta subunits. Of the unfractionated thymocytes, 88% +/- 5 SD and 56% +/- 8 SD were labeled by H38 and H36, respectively. More than 90% of cells in cluster of differentiation (CD)-1+ (mainly cortical) and CD1-CD3+ (mainly medullary) subsets were stained with H38. When tested by H36, 51% +/- 6 SD of CD1+ and 81% +/- 8 SD of CD1-CD3+ thymocytes were positive. In the immature CD3-CD1- subpopulation, less than 3% of cells reacted with H36, whereas 15% +/- 3 SD were stained by H38. Flow cytometry revealed that CD1+ (mainly cortical) thymocytes expressed CD3 surface antigen in a percentage similar to that of CD1+ cells positive for Ti-alpha subunits. Indirect double labeling procedures with immunogold- and peroxidase-conjugated second antibodies demonstrated that almost all CD1+/Ti-alpha + cells expressed the surface CD3 antigen, whereas a large proportion of CD1+/Ti-beta + cells did not. These results indicate a sequential expression of Ti-beta and Ti-alpha subunits during intrathymic T cell differentiation. They also suggest that assembly and surface expression of the CD3-Ti complex are linked to the production of Ti-alpha-chains in addition to Ti-beta subunits. Last, the expression of Ti-alpha and Ti-beta subunits was studied in peanut agglutinin (PNA)+, CD1+ blasts representing the main, spontaneously proliferating intrathymic pool. The lack of Ti-alpha and Ti-beta subunits and the absence of surface CD3 antigen on most of these blasts suggest that immature T cells are compelled to proliferate in the thymus in a CD3-Ti complex independent manner.     

Frequency analysis of immunoglobulin V-gene expression and functional reactivities in bone marrow B cells

Frequency of immunocompetent B cells in bone marrow has been determined in vitro under culture conditions that allow the development in vitro under culture conditions that allow the development of every growth-inducible B cell into a clone of IgM-secreting PFC. Three limiting dilution culture systems were employed: a specific helper assay with SRBC as antigen and using activated T helper cells, a nonspecific helper assay using Con A-induced factors as a source of help, and polyclonal activation with LPS. From unseparated, normal C57BL/6J bone marrow 1 in 2200 to 1 in 2820 B cells were induced to form a clone of PFC to SRBC in each of the 3 systems. This corresponds to a frequency of 1 SRBC-specific clone in every 900 IgM-secreting LPS-reactive clones. The frequencies of specific plaque-forming B cell clones in terms of LPS-reactive B cells was 1 in 36 for NNP1-SRBC, 1 in 58 for TNP30-SRBC, 1 in 75 for NIP1-SRBC, and 1 in 230 for TNP3-SRBC. These frequencies of v-gene expression in bone marrow B cells are of the same magnitude as the corresponding frequencies for splenic B cells. Bone marrow B cells are also fully susceptible to stimulation by antigen in combination with either specific or nonspecific T cell help, as well as polyclonal activation by LPS, since every 3rd Ig-positive cells in marrow could be induced to form a clone of IgM-secreting cells. There is thus no difference in immunocompetence between surface Ig-bearing B cells from bone marrow and spleen.     

Activation of T cells in tumor-bearing mice

Subcutaneous transplantation of the syngeneic P815 mastocytoma in DBA/2J mice induced an activation of splenic T cells which resulted in a hyperresponsiveness of the tumor-bearing animal to the unrelated antigens pneumococcal polysaccharide (Pn) and sheep red blood cells (SRBC). These tumor-activated T cells appeared to increase the plaque-forming cell (PFC) potential of suboptimal numbers of spleen cells, caused normal spleen cells to express increased numbers of PFC, and produced lymphokine(s) which also increased PFC responses of normal splenocytes. The tumor-activated T cells responsible for stimulating normal splenocytes in an in vitro antibody response were shown to be Ly+2- cells. The activity of the tumor-activated T-cell supernatants was not genetically restricted and required additional Ly1 T cells in order to induce rigorously clean B cells to produce antibody. The T cells capable of stimulating non-specific antibody responses were also capable of slowing tumor growth when injected with tumor cells in normal recipient mice. These results suggest that T cells activated by tumor antigens release immunostimulatory lymphokines and, at the same time, are capable of leading to inhibition of tumor growth.     

Human helper-T-cell function does not require T4 antigen expression

The relationship between immunoregulatory T-cell function and the expression of T-cell subset-specific differentiation antigens was examined using a phenotypically anomalous human T-cell line (TCL), termed H-1. H-1 cells were found to express T11, extremely high levels of T3, but no T4 nor T8 antigen. Despite their lack of T4 antigen expression, H-1 cells could be activated by coculture with pokeweed mitogen (PWM), anti-T3 antibody, or autologous B cells to provide potent help for B-cell differentiation into plaque-forming cells (PFC). In contrast, H-1 cells did not suppress the PFC response triggered by PWM-activated T4+ cells. These results demonstrate that the expression of the T-cell subclass-specific differentiation antigen, T4, is not required for a T cell to become activated and to implement the program for helper function. In addition, enhanced expression of T3 on the T4-, T8-, H-1 cell surface may reflect a compensatory upregulation of the T3/Ti receptor complex on T cells which are deficient in these nonpolymorphic associative recognition structures.     

Regulation of T15 idiotype dominance. II. Genes unlinked to the Igh locus regulate T15 dominance of the secondary adoptive transfer response to phosphocholine

We have studied the idiotype and fine specificity of the secondary immune response to phosphocholine (PC) in C57BL (B10, B10.D2, and B.C8) and BALB (BALB/c, BAB-14, and C.B20) congenic strains of mice. In vivo IgM responses of mice from these two genetic backgrounds differed in their T15 idiotypic representation. BALB strains expressed the T15 idiotype on greater than 90% of their IgM, PC-specific plaque-forming cells (PFC), whereas C57BL strains expressed the T15 idiotype on approximately 50% of their IgM PFC. All strains examined expressed greater than 75% PC-inhibitable, VHPC idiotype-positive, IgM PFC. The IgG3 and IgA memory responses were similar to the IgM memory response; BALB strains produced a higher proportion of T15+ PFC than C57BL strains; however, the majority of IgG3 and IgA PFC in all strains were VHPC+, and PC-inhibitable. In contrast, the IgG1 memory response was not dominated by T15+, VHPC+, PC-inhibitable PFC in any of the strains tested. The IgG1 PFC required nitrophenylphosphocholine (NPPC) for efficient inhibition. The IgG2 memory response generally mimicked the IgG1 response with respect to idiotype and specificity. These data demonstrate that the representation of the T15 idiotype in the anti-PC immune response is determined by genes outside both the MHC and Igh genetic loci. Control of T15 expression in secondary IgM, IgG3, and IgA anti-PC responses was examined by using a cell-mixing protocol with primed T and B cells from BALB/c and B10.D2 mice. T15 representation in these responses was determined by the genotype of the B cell, not by the genotype of the helper T cell. Similarly, the B cell genotype was responsible for the idiotypic profile of a primary, in vitro, T-dependent, anti-PC response.