IgD Receptors of Lymphoid Cells

While present in normal human serum in very low amounts and undetectable in sera of non-human primates as well as of mice, IgD is found on the surface of the majority of B lymphocytes in all the above mentioned species.

Lymphocytes which carry IgD on their membrane also have IgM. The two molecules are present in relative amounts that can be very different in different cells.

Both IgM and IgD of a single cell are the actual product of the cell itself. They have the same light chain and, more importantly, the same combining site and idiotype.

IgD/IgM bearing lymphocytes are the majority of all B lymphocytes in spleen, lymph nodes and Peyer's patches, whereas in bone marrow they account for half of the immunoglobulin positive cells. Although the percentage of double IgD/IgM cells is very similar in different tissues, the total amount of IgD, as well as the relative amounts of IgD and IgM as detected by biochemical methods varies. In fact, lymph nodes, and even more Peyer's patches are much richer than spleen in cells having levels of IgD higher than those of ISM; conversely, in the bone marrow, all the positive cells have very low levels of IgD.

In ontogeny, as in evolution, IgD appears after IgM: in human foetuses IgD bearing cells are not detectable before 13 weeks of gestation, and in the muse they appear only after birth.

IgD receptors seem to disappear from B cells which undergo maturation to secretion, as indicated by the fact that only a proportion of IgM secreting plasma cells show membrane IgD.

IgD is never found on the membrane of IgG-containing cells, and also lymphocytes bearing simultaneously IgD and IgG are very rare, and it might well be that for these cells, the double expression for short periods of time does not actually correspond to simultaneous synthesis.     

Suppressor Activity of T Cells Bearing Fc Receptors for IgG on Lymphoid Colony Formation

Human T lymphocytes, upon phytohaemagglutinin stimulation, are able to form colonies in semisolid media. Peripheral T cells bearing Fc receptors (T_G) were studied for their possible regulatory activity on lymphoid colony development. Although no substantial differences were observed between the cloning efficiency of unfractionated T cells (thus including T_G cells) and T cells depleted of T_G, a sharp suppression of colony formation occurred when positively selected T_G cells were readded to T_G-depleted suspensions. Therefore, T_G suppressor activity seems to be strictly dependent upon cell interaction with ox IgG immune complexes used for T_G cell isolation. Different experimental approaches failed to demonstrate, although did not exclude, that suppression in this system is mediated by soluble factors, γ-irradiation of T_G cells abrogated their suppressor capacity.     

Electrophoresis of Lymphoid Cells

The electrophoretic mobility of small lymphoid cells in the thymus, lymph nodes, and spleen was measured. The distribution patterns were organ specific. The majority of the thymic cells were slow with a small 'tail' of faster cells. Both lymph node and spleen cells showed a fast and a slow cell population with a difference in mean electrophoretic mobility of about 40%. The percentage of cells to the fast and slow groups was similar to the percentage of T- and B-cells in these organs It is therefore suggested that T-and B-cells may be characterized by their different electrophoretic mobilities and also that there may be a change in the net surface charge during maturation from thymocyte to T-lymphocyte.     

Interaction Between a Synthetic Polypeptide, TIGAL, and Fc Receptors on Non-Bursa-Derived Chicken Lymphoid Cells

Autoradiographic studies have shown that radioiodinated TIGAL binds in vitro to a small but varying fraction of lymphoid cells from bursectomized, agammaglobulinemic chickens, whereas no binding of radioiodinated TGAL or a variety of other radioiodinated antigens can be observed. The binding of [125I]TIGAL is inhibited by antigen-antibody complexes. Radioiodinated antigen-antibody complexes are bound to a similar proportion of the lymphoid cells from bursectomized chickens, and this binding is inhibited by preincubation of the cells with unlabeled TIGAL but not with TGAL. These results indicate a cross-reaction at the level of Fc receptors between determinants on TIGAL and on IgG.     

Localization in Mouse Lymphoid Tissue of Receptors for Immunoglobulin

Cryostat sections of mouse spleen and lymph nodes adsorbed sheep erythrocytes coated with rabbit or mouse IgG antibody. The reaction was mediated by the Fe part of the immunoglobulin molecule. Haemadsorption was inhibited by mouse IgG and antigen-antibody complexes. Complement was not required.
Sensitized erythrocytes failed to bind to thymus and to the thymus dependent areas of the peripheral lymphoid tissue. Results of Inhibition experiments with rabbit anti-mouse lymphocyte serum and anti-Θ serum further suggested that binding of sensitized erythrocytes to lymphoid tissue sections can be used as a marker for B lymphocytes.     

Presence of Receptors for IgD on Human T and Non-T Lymphocytes

Ig-coated latex particles were used to study the presence in human blood of lymphocytes with receptors for various Ig classes. A significant proportion of cells bound to particles coated with IgG, IgA and IgM. In addition, 0–6.5% (mean 2.2%) peripheral blood lymphocytes from normal blood donors were able to form rosettes with IgD-coated latex particles. Inhibition studies showed that the latter receptors were distinct from those directed against IgG, IgA and IgM. IgD receptor-bearing cells seemed to exist both among T cells and non-T cells but were 3–10 times more frequent in the non-T-cell population.     

Effect of Neuraminidase on Lymphoid Cells

After neuraminidase treatment the electrophoretic mobility of mouse lymphocytes (B and T cells) and thymocytes was reduced to a similar value, .a diminution of about 40%, 60%, and 40%, respectively. Thus B and T cells and thymocytes may have a common surface charge after removal of sialic acid. The percentage of cells binding anti-thymocyte serum was not changed; thus sialic acid does not seem to be an important part of the specific antigen of lymphoid cells. Similar amounts of sialic acid were released from B and T Ceils, whereas less than half of this was released from the thymocytes. Thus, whereas thymocytes are characterized by their low electrophoretic mobility and low sialic acid release and T cells by high electrophoretic mobility and high sialic acid release, B-cells in contrast show a low electrophoretic mobility and high sialic acid release.     

Localization of IgGFc and Complement Receptors in Chicken Lymphoid Tissue

Chicken lymphoid organs were examined for IgGFc and complement receptors (FcR/CR) by immune adherence on frozen tissue sections. Indicator systems were sheep erythrocytes (E) coated with chicken anti-E IgG (Each). E coated with rabbit anti-E IgG (EArab) and normal chicken serum (EAC), and FITC-labelled zymosan particles coated with chicken serum (ZyC). In the spleen, FcR and CR activity was confined to B-dependent areas, i.e. the periellipsoidal sheaths and germinal centres and the red pulp. No FcR were found in the thymic or bursal lymphoid tissue, but CR activity was observed in the medulla of bursal follicles. Chicken and turkey IgG, chicken IgGFc, and bovine serum albumin (BSA)-chicken anti-BSA complexes inhibited binding of EAch. No inhibition was obtained with chicken IgGF(ab')₂. IgM or albumin, or with BSA-rabbit anti-BSA complexes and human or rabbit IgG. E did not adhere to the sections, nor did EArab, EArab incubated with heat-inactivated chicken serum, or EAC complexes prepared with EArab and guineapig complement. The data suggest that chicken B lymphocytes and macrophages have receptors for avian IgGFc and C which can be demonstrated in tissue sections.     

T and B Cells in Various Lymphoid Tissues in Mice: Membrane Immunofluorescence with Purified Lymphoid Cells

The proportion of T and B cells in several lymphoid tissues of the mouse was determined by membrane immunofluorescence. Lymphoid cell preparations were purified by glass-wool column and Hypoque-Ficoll sedimentation to eliminate the large majority of non-lymphoid cells which might introduce counting errors on fluorescence microscopy. FITC-labelled horse anti-mouse-globulin did not stain thymocytes (T cells) whereas it did stain a proportion of the lymphocytes of other lymphoid tissues (B cells): peripheral blood, 11%; bone marrow, lymph node, 23%; spleen, 24%. These results correlated well with the proportion of cells stained by anti-B cell sera obtained by the complete absorption of anti-lymphocyte serum (ALS) with thymocytes.     

Phenotypes of ''Null'' Lymphoid Cells in Human Blood

F(ab')2 antibody fragments of heteroantisera directed against p28,33 (or 'Ia-like') antigen, T-cell antigen(s) (T), myeloid antigen (M), and immunoglobulin have been used along with rosetting techniques to analyse the antigenic heterogeneity of 'null' or 'unclassified' lymphoid cells purified 'negatively' from human blood by E rosette depletion of T cells and B removal on an anti-immunoglobulin immunoabsorbent. The results confirm that considerable heterogeneity exists within the 'null' cell population; the majority of cells are p28,33+ and Fcgamma-receptor-positive, and a proportion but not all of these p28,33+, Fcgamma+ cells are also C3-receptor-positive but negative for the other heteroantigens (T and M). 2-6% were 'pre-B' by the criteria of immunofluorescent staining for cytoplasmic IgM in the absence of detectable cell surface Ig. 1-3% stained intensely with anti-IgM, anti-IgG or anti-IgA, or anti-k plus anti-lambda and were presumed to be plasma cells or their immediate precursors. No null cells stained with antibody to terminal deoxynucleotidyl transferase enzyme, a marker for early T lineage cells, and less than 1% expressed an acute ('non-T, non-B') lymphoblastic-leukaemia-associated membrane antigen which is believed to be an 'early' lymphoid lineage differentiation marker. A minor subpopulation made sheep 'E' rosettes, and another made mouse 'E' rosettes after neuraminidase pretreatment of the lymphoid cells. A small proportion of 'lymphoid', 'null cells' were reactive with an anti-myelomonocytic (M) antibody. It is suggested that 'null' lymphoid cells in blood are heterogeneous and that most are not immature T or B precursors but either a relatively mature B lymphocyte population with a very low density of membrane immunoglobulin or a distinct non-T, non-B cell type.     

Derivation of Dendritic Cells from Myeloid and Lymphoid Precursors

The antigen presenting dendritic cells (DC) found in mouse and human lymphoid tissues are heterogeneous. Several subsets of mature DC have been described and these may correspond to distinct lineages. In this review, we present evidence obtained from a series of studies on the lineage origin of DC. This evidence points to the existence of at least three pathways for DC development, namely one from mycloid progenitors, a second from lymphoid progenitors and the third for Langerhans cells from precursors whose relationship to myeloid or lymphoid cell types is not yet clearly defined.