Active suppression of immunoglobulin allotype synthesis. 3. Identification of T cells as responsible for suppression by cells from spleen, thymus, lymph node, and bone marrow

Thymus-derived cells (T cells) that actively suppress production of IgG2a immunoglobulins carrying the Ig-1b allotype have been found in adult (SJL x BALB/c)F(1) mice exposed to anti-Ig-1b early in life. The suppression is specific for Ig-1b. The allelic product, Ig-1a, is unaffected. Spleen, lymph node, bone marrow, or thymus cells from suppressed mice suppress production of Ig-1b by syngeneic spleen cells from normal F(1) mice. When a mixture of suppressed and normal cells is transferred into lethally irradiated BALB/c mice, there is a short burst of Ig-1b production after which Ig-1b levels in the recipient fall rapidly below detectability. Pretreatment of the cells from the suppressed mice with antiserum specific for T cells (anti-Thy-1b) plus complement before mixture destroys the suppressing activity. Similar results with suppressor cells were obtained in vitro using Mishell-Dutton cultures. Mixture of spleen cells from suppressed animals with sheep erythrocyte (SRBC)-primed syngeneic normal spleen before culture suppresses Ig-1b plaque-forming cell (PFC) formation while leaving Ig-1a PFC unaffected. Treatment of the suppressed spleen with anti-Thy-1b before transfer removes the suppressing activity.

Demonstration that antigen-binding cells are precursors of antibody-producing cells after purification with a fluorescence-activated cell sorter

We have obtained viable and functional populations of antigen-binding cells enriched up to 500-fold from primed spleen-cell suspensions by fluorescent labeling and by a new electronic cell sorter that sorts viable cells according to fluorescence. Concomitantly, populations largely depleted of antigen-binding cells were obtained. While neither population alone is capable of a full adoptive secondary response when injected into irradiated recipients, a reconstituted mixture restores the full response of the unfractionated spleen cells. Admixture of sources of unprimed thymus-derived cells (T-cells) with the purified antigen-binding cells (B-cells) restores much of the full response.

Active suppression of immunoglobulin allotype synthesis. II. Transfer of suppressing factor with spleen cells

The mechanism of chronic allotype suppression in (SJL x BALB/c)F(1) mice has been investigated by means of cell transfer studies. These mice are phenotypically negative for serum Ig-1b, the paternal allotype determinant on gammaG(2a) immunoglubulin, as a result of perinatal exposure to maternal anti-Ig-1b. When spleen or bone marrow (B) cells from suppressed mice were injected into irradiated BALB/c "indicator" hosts, detectable levels of Ig-1b were demonstrated in the sera of a majority of the recipients early after transfer. These results indicate that Ig-1b-producing cells or their precursors are present in the lymphoid tissues of suppressed mice, even though they are not expressed. Within 5-7 wk, it was no longer possible to detect Ig-1b in the sera of these hosts, although cells producing another paternal allotype (Ig-4b) were shown to persist. Control BALB/c mice, injected with spleen and B cells from normal mice, continued to produce high levels of immunoglobulin carrying this allotype. The disappearance of serum, Ig-1b occurred most frequently in the recipients of suppressed spleen cells. Similar results were obtained using a mixture of spleen cells from normal and suppressed mice. Ig-1b production in the recipient mice ceased within a few weeks, even though the majority of cells in the mixture were obtained from normal (nonsuppressed) donors. The data are interpreted as evidence that chronic allotype suppression in mice is actively maintained by cells which are resident in the lymphoid tissues, splenic cells being the most effective. These cells are capable of proliferating in a new host and exerting their suppressive influence on Ig-1b-producing cells and/or their precursors.

Active suppression of immunoglobulin allotype synthesis. I. Chronic suppression after perinatal exposure to maternal antibody to paternal allotype in (SJL x BALB-c)F 1 mice

Long-term (chronic) allotype suppression, previously reported only in rabbits, is shown here to occur in at least one strain combination of mice as well. Close to 50% of the offspring of SJL (Ig(b)) males mated to BALB/c (Ig(a)) females immunized against the paternal allotype were found to be suppressed for Ig-1b (gammaG(2a)) at 6 months of age. These mice are called "chronically" suppressed. The percentage of offspring in this strain combination suppressed for the paternal allotype at 8 wk of age is the same as that seen in an earlier strain combination tested, [(C57 x BALB/c)F(1)], in which all mice recover from suppression by 10-12 wk. After 8 wk, two distinct patterns of long-term (chronic) suppression emerge in (SJL x BALB/c)F(1) mice: a small number of these mice never produce detectable amounts of Ig-1b throughout their lives, while the majority produce detectable Ig-1b sporadically, sometimes over a period of several weeks, the level of which eventually falls below detectability. Attempts to "cure" suppression by destroying the existent lymphoid population and forcing endogenous repopulation in chronically suppressed animals were unsuccessful. Furthermore, attempts to restore Ig-1b production by injection of cells from syngeneic Ig(a)/Ig(b) donors into irradiated, chronically suppressed recipients were also unsuccessful, although the same cell inocula, when injected into irradiated BALB/c (Ig(a)/Ig(a)) mice produced high levels of gamma globulin carrying the allotype. These results suggest that long-term allotype suppression resulting from perinatal exposure of offspring to specific anti-allotype antibody (anti-Ig-1b), is not due merely to an absence of Ig-1b-producing cells or their progenitors, but appears to be an active process, which dominates physiologically over normal production.

Immunological memory in mice. 3. Memory to heterologous erythrocytes in both T cell and B cell populations and requirement for T cells in expression of B cell memory. Evidence using immunoglobulin allotype and mouse alloantigen theta markers with congenic mice

Using anti-allotype sera and AKR anti thetaC3H sera, a requirement for two cell types has been demonstrated in the adoptive secondary response of mice to heterologous erythrocytes. The cell types have been designated B cells [precursors of plaque-forming cells (PFC)] and T cells (thymus-influenced cells, not providing precursors of detectable PFC). The in vivo indirect PFC response of spleen cells from primed mice is markedly reduced by in vitro treatment of the cells with a mixture of anti-theta serum and guinea pig serum (Anti theta + GPS). This B cell response is fully restored to control levels by thymus cells from normal mice which do not themselves provide precursors of indirect PFC. Thus memory is carried by the B cell lineage but the expression of this memory is dependent on the presence of a cell population which is sensitive to Anti theta + GPS and which is replaced functionally by unprimed T cells. When assayed for T cell activity, thoracic duct cells from specifically primed mice are better than cells from nonspecifically primed mice in restoring the B cell response of spleen cells from immunized mice. Moreover, the T cell activity of a reconstitutive cell population from primed mice is reduced by incubation with Anti theta + GPS. We conclude that memory to heterologous erythrocyte antigens is carried by the T cell lineage as well as the B cell lineage even though unprimed T cells are sufficient for expression of B cell memory.

Tolerance and immunity to maternally derived incompatible IgG 2a -globulin in mice

Progeny mice were confronted with maternal gamma-globulin of a different allotype by either back-cross mating, intercross mating, or by foster nursing. In all cases, many mice subsequently produced alloantibodies directed against the incompatible maternal type of IgG(2a)-globulin. In one series of experiments, immunologic tolerance to the maternally derived gamma-globulin was demonstrated to exist in the period before formation of spontaneous antibody. The state of tolerance was then lost, unless maintenance injections of foreign gamma-globulin were given. These studies demonstrate in a natural situation that maternally derived foreign proteins can first induce a state of immunological tolerance which is followed, after disappearance of the antigen, by a state of immunity. As such, this parallels the experimental induction of tolerance to foreign proteins by neonatal injections.

Mouse lysozyme production by a monocytoma: isolation and comparison with other lysozymes

A transplantable mouse tumor, GPC-11, produces large amounts of lysozyme. The tumor is a reticulum cell sarcoma, type A, and is a neoplasm of monocytes. The lysozyme was purified from mouse urine in quantities sufficient for structural analysis. Comparison of mouse lysozyme with lysozymes from; chicken egg white and patients with monocytic leukemia reveals similarities in size and electrophoretic mobility and, with human lysozyme, in functional properties; but considerable differences are found in antigenic characteristics and amino acid composition.

Immunological memory in mice. II. Cell interactions in the secondary immune response studies by means of immunoglobulin allotype markers

Congenic mice, differing genetically only at the loci coding for immunoglobulin H chain (or Fc) structures, have been used to study cell interactions in the 7S (gammaG(2a)) antibody response to sheep erythrocytes (SRBC), as detected by the Jerne plaque-forming cell (PFC) method. The interaction between thymus and bone marrow cells was studied in adult thymectomized irradiated recipients, protected with syngeneic bone marrow and injected with thymus cells from the partner congenic strain. All of the gammaG(2a) PFC detected in the spleens of these mice were of bone marrow allotype. Adoptive secondary immune responses were then studied to determine whether a similar interaction between memory cells and bone marrow derived cells could be detected. Primed spleen cells from the partner congenic strain, or a subpopulation of these cells obtained by BSA density gradient fractionation, were injected into irradiated recipients alone, or together with syngeneic nonimmune spleen or bone marrow cells. All gammaG(2a) PFC detected in these experiments were of primed cell allotype. There was no evidence that antibody forming cell precursors in normal spleen or bone marrow participate in the adoptive secondary immune response detected 7 days after transfer of primed spleen cells. This was true regardless of whether the bone marrow cells were injected at the time of transfer, or were injected 1-2 wk earlier and allowed to become established in the spleens of recipient mice. Although no specific cell interaction was seen, bone marrow (and, to a lesser degree, normal spleen) cells were found to have a nonspecific enhancing effect on the adoptive secondary response when they were injected together with the primed spleen cells. This enhancement was not evident if the bone marrow cells were injected 1 or 2 wk prior to primed cell transfer.

Immunological memory in mice. I. Physical separation and partial characterization of memory cells for different immunoglobulin classes from each other and from antibody-producing cells

Plaque forming cells (PFC) of different immunoglobulin classes producing antibodies against sheep erythrocytes were separated according to their buoyant densities by means of equilibrium centrifugation in a stepwise BSA gradient. In the period of 7-10 days after immunization gammaM PFC are markedly enriched in fractions of low density and relatively depleted in fractions of high density. The distribution of total gammaG PFC shows less enrichment in the lower density fractions and less depletion in the higher density fractions. The density profile for gammaG(2a) PFC is even flatter, with a significant difference (depletion) relative to the unseparated spleen cells only in the highest density fraction. The density gradient distributions of cells able to transfer an adoptive immune response of the various immunoglobulin classes are markedly different from the PFC distribution. Cells obtained 7-10 days after immunization able to transfer an IgM response are present in the same proportions across the density gradient, whereas memory cells for gammaG(2a) obtained at this time are markedly enriched in fractions of low density and virtually depleted from high density fractions. With increasing time after primary immunization, the gammaG(2a) memory cells increase progressively in density and by 6 weeks the higher and lower density fractions have the same proportions of gammaG(2a) memory cells. The total gammaG (mainly gammaG(1)) memory cells by 7-10 days show slight enrichment in low density fractions and no depletion in high density fractions. The conclusions were reached that (a) memory for gammaG(1) develops earlier than memory for gammaG(2a) and (b) that memory for anti-SRBC antibodies of different classes is carried in separate cells. When gradient fractions enriched for PFC and memory cells for all classes were completely depleted of PFC using glass bead columns, the ability of this fraction to transfer memory for all classes was not diminished. This shows that memory cells are not identical with cells secreting antibodies.

Cell sorting: automated separation of mammalian cells as a function of intracellular fluorescence

A system for high-speed sorting of fluorescent cells was able to sort mouse spleen cells from Chinese hamster ovarian cells after development of fluorochromasia. Highly fluorescent fractions separated after similar treatment from mouse spleen cells immunized to sheep erythrocytes were enriched in antibody-producing cells by factors of 4 to 10.