Search PubMed⌕ Search

Biomedical subjects

F Loor

Publications and source records attributed to F Loor.

At least 109 records · Page 6Linked to original sources
PubMed1976

Immature T lineage lymphocytes in athymic mice. Presence of TL, lifespan and homeostatic regulation.

Lymphocytes belonging to the T lineage were described in athymic nude mice. We showed previously that they were distinguished from usual peripheral lymphocytes by their low density of theta antigen, their slow electrophoretic mobility and their absence of recirculation through the thoracic duct. We now report that they also express the TL antigen, have a life span of 1 to 2 days, are produced in the bone marrow and are under the homeostatic influence of the thymus. Indeed they appear rapidly in surgically T-deprived mice and their production is blocked in both surgically or congenitally athymic mice receiving a thymus graft. This homeostatic control may be mediated via a humoral factor. Cells with similar characteristics are present in the thymus at early stages of embryogenesis. The characteristics of these T lineage lymphocytes strongly suggest that they may represent "pre-thymocytes", i.e. cells already committed to the T pathway independently of thymic influence but needing the thymus microenvironment to differentiate further.

Animals↗
PubMed1976

T lineage lymphocytes in nude mice born from homozygous nu/nu parents.

T lineage cells are found in the spleen of neonatal nu/nu mice born from nu/nu x nu/nu matings, and also in old, healthy nude mice obtained from the usual nu/+ x nu/nu matings. Their presence in neonatal nude mice which were never in contact with mother or normal littermate thymus products shows that commitment of stem cells towards the T lineage does not require the influence of the thymus.

Aging↗
PubMed1975

Immunofluorescence studies of a possible prethymic T-cell differentiation in congenitally athymic (nude) mice.

A rabbit antimouse brain theta reagent was made specific for cells of the T lineage by absorption in vivo in nude mice. When used in double fluorescence together with an antimouse immunoglobulin reagent, four types of cells were found in spleen and lymph nodes of both normal and nude mice: Ig+thetaBr-, Ig-thetaBr+, Ig-thetaBr-, and Ig+thetaBr+. The data show that about 20% of nude mouse spleen lymphocytes are definitely of T lineage (Ig-thetaBr+). On these cells, the detection of the "thetaBr" determinant, which is identical or very close to the "theta" determinant, depends on the large amplification produced by indirect immunofluorescence, which suggests a low density of theta antigen. Similar experiments suggest the presence of cells that express some TL antigen in the spleen of nudes made congenic to a TL+ strain (BALB/c). It is proposed that the T-cell precursor that will further differentiate in the thymus already expresses a low density of theta and, in TL+ strains, TL antigen.

Animals↗
PubMed1975

Five types of lymphocytes (Ig-theta-, Ig-theta+weak, Ig-theta+strong, Ig+theta- and Ig+theta+) characterized by double immunofluorescence and electrophoretic mobility. Organ distribution in normal and nude mice.

The simultaneous detection of Ig and theta on the surface of mouse lymphocytes permits the detection of four cell types (Ig-theta-, Ig-theta+, Ig+theta-, and Ig+theta+) which also have distinct electrophoretic profiles. All types are present in variable proportions in all lymphoid organs studied. Results obtained in congenitally athymic nude mice and in T-deprived mice define a new type of lymphocyte, the Ig-theta+weak. This cell is non-recirculating, Ig-, with a low density of theta and a slow electrophoretic mobility. It is a candidate for a T-committed prethymic cell.

Animals↗
PubMed1975

Development of surface immunoglobulins in the chicken.

B-cell maturation in the chicken has been evaluated by the appearance of membrane immunoglobulins on cells in the spleen, the thymus, the bursa and the bone marrow during enbryonic development and shortly after hatching. The majority of the bursa cells acquire demonstrable membrane immunoglobulin between days 16 and 18 of incubational age and show significantly increased amounts of membrane immunoglobulin between days 18 and 20, even though immunoglobulin-bearing cells can be found in the bursa as early as day 14 of enbryonic age. The spleen shows cells possessing immunoglobulin receptors can their membranes (Ig+) only after the bursa cells have reached full membrane immunoglobulin maturation as reflected in the number of Ig+ cells and the amounts of membrane immunoglobuline. The thymus is practically devoid of Ig+ cells in the embry and it is not clear whether there any Ig-+ cells in the bone marrow. There are two phenomena which stand out in the observations. One is that there appears to be a gradual increase in the quantity of quality of the surface immunoglobulins on individual cells with advance in the embryonic development as reflected in the gradual increase in the staining intensity. The other is that there appears to be a polar distribution of membrane immunoglobulin in some cells especially in younger embryos. This polar distribution is seen under conditions where immunoglobulin capping is prevented by inhibitors and where immunoglobulin capping is impossible, such as with monomeric Fab. Immunoglobulin capping has been found to occur readily in embryonic cells and under conditions which would normally inhibit capping in adult cells.

Animals↗
PubMed1974

Activity of host-derived T cells which differentiate in nude mice grafted with co-isogenic or allogeneic thymuses.

If nude mice are grafted with a neonatal thymus, host type precursor cells develop within the graft thymus and after about 6 wk the T-cell population of the thymus, spleen, and lymph nodes is of host type. However, immunological responsiveness produced in nude mice in this manner is incomplete: (a) the ability to react to T-cell mitogens in vitro is greater than in untreated nudes but lower than in normal mice; (b) the response to T-cell dependent antigens is less than normal; and (c) the rejection of skin grafts is slower than in normal animals. Whether host precursor cells which differentiate in an allogeneic thymus are able to reject skin grafts from thymus donor strain appears to depend on the strain combination used.

Animals↗
PubMed1973

Differentiation of T-cell precursors in nude mice demonstrated by immunofluorescence of T-cell membrane markers.

When the thymus from an AKR mouse (TL(-), theta-AKR) is grafted to a BALB/c-nu/nu mouse (TL2, theta-C3H), the grafted thymus is rapidly repopulated by host lymphocytes, i.e., lymphocytes having the TL2 and theta-C3H T-lymphocyte membrane antigen markers. theta-C3H lymphocytes also appear rapidly in the spleen and lymph nodes. After a few weeks, BALB/c nude mice grafted with AKR thymus and normal BALB/c mice could not be distinguished on the basis of the number of TL-positive thymocytes or theta-C3H-positive lymphocytes in thymus, spleen, or lymph nodes. These experiments give a definitive proof of the existence of precursor cells for the T compartment of the lymphoid system in the nude mouse. They strongly suggest the involvement of host-derived T cells in the recovery of some T-cell functions by nude mice grafted with allogeneic thymuses.

Animals↗