Optimal conditions for the generation of monoclonal antibodies using primary immunisation of mouse splenocytes in vitro under serum-free conditions

Independent differentiation of mammotropes and somatotropes in the chicken embryonic pituitary gland. Analysis by cell distribution and attempt to detect somatomammotropes

It has been reported that mammotropes in a rodent pituitary gland are derived from somatotropes via somatomammotropes (SMTs), cells that produce both growth hormone (GH) and prolactin (Prl). However, no studies have been done on the transdifferentiation of somatotropes in the chicken pituitary gland. In this study, in order to determine the origin of mammotropes, we studied detail property of appearance of chicken somatotropes, mammotropes and pit-1 cells and then evaluated the existence of SMTs in the chicken embryonic pituitary gland. Immunohistochemical analysis revealed that GH-immunopositive (GH-ip) cells appeared on embryonic day (E) 14 and were mainly distributed in the caudal lobe, while Prl-immunopositive (Prl-ip) cells appeared in the cephalic lobe of the pituitary gland on E16. In situ hybridization (ISH) and RT-PCR analysis showed that expression of GH and Prl mRNA starts at E12 in the caudal lobe and at E14 in the cephalic lobe respectively. Pit-1 mRNA was first detected on E5 by RT-PCR, and pit-1 mRNA-expressing cells were found in the cephalic lobe on E8. Then with the ontogeny of the chicken, these cells spread into both lobes. Using a double staining method with ISH and immunohistochemistry, we could not detect the existence of SMTs in the chicken embryonic pituitary gland even in the marginal region of either lobe. These results suggest that chicken somatotropes and mammotropes independently appear in different lobes of pituitary gland and that transdifferentiation from somatotropes to mammotropes is not the central route for differentiation of mammotropes in the embryonic chicken pituitary gland.

Reduction of animal use in human vaccine quality control: opportunities and problems

In vivo assays play a crucial role in the assessment of the potency and safety of human vaccines. Robust vaccine production procedures, improved characterisation methods and development of well-characterised vaccines create possibilities to reduce animal use. In this paper the current status in this field is reviewed. Achievements with regard to in vivo and in vitro potency and safety testing are discussed as well as new developments and possibilities in the field of in vitro characterisation of vaccine components. Finally, validation and implementation issues will be dealt with. Although replacement of in vivo tests for batch release of existing vaccines is difficult, emerging technologies allow well-considered reduction of in vivo experiments during product and process development and improvement. Inextricably bound up with this approach is good manufacturing practice (GMP), resulting in robust, validated production processes.

Immunohistochemical evidence that follicle-stimulating hormone and luteinizing hormone reside in separate cells in the chicken pituitary

As is the case in other tetrapod species, the chicken gonadotropins LH and FSH consist of a common alpha subunit and a hormone-specific beta subunit. Gonadotrophs containing LH were shown earlier to be distributed throughout both the caudal and cephalic lobes of the chicken anterior pituitary, but the cellular distribution of FSH in avian species is still uncertain. The purpose of this study was to determine the cellular distribution of FSH-containing chicken gonadotrophs by use of FSH-specific monoclonal antibodies (mAbs). Three new mAbs toward chicken FSH were proven hormone specific by immunodetection of purified hormones on dot blots and by dual-label immunohistochemistry (IHC) on sagittal sections of chicken pituitaries. A rabbit antibody was used to detect chicken LH. Results showed that LH-containing gonadotrophs were densely distributed throughout the anterior pituitary, whereas gonadotrophs containing FSH were much less numerous; in addition, while also present in both lobes, FSH-positive cells were largely absent from the outer margin of the gland. Dual-label IHC revealed that LH and FSH reside almost exclusively in separate gonadotrophs. The identity of FSH-containing cells was further confirmed through use of an antibody to the chicken alpha subunit, which showed that FSH immunoreactivity was always colocalized with the alpha subunit. Our results suggest the possibility that production and secretion of LH and FSH may be regulated differently in chickens than in most other species studied to date.

The molecular characterisation of chicken pituitary N-terminal pro-opiomelanocortin (POMC)

Monoclonal antibodies (Mabs) specifically recognizing the chicken pituitary corticotropes were used to isolate a population of closely related peptides from crude chicken pituitary extracts. A homogeneous N-terminal sequence homologous to the extreme N-terminus of mammalian and amphibian pro-opiomelanocortin (POMC) was revealed. Further physicochemical analysis proved the existence of a series of C-terminally truncated peptides including 3 major molecular species corresponding to Ser1-Gly64, Ser1-Arg73 and Ser1-Gly105 respectively. The two latter molecules were shown to be N-glycosylated at position Asn67, with mass spectrometric data indicating a carbohydrate structure of the oligomannose 5 type, in addition to two more complex structures. No evidence was found in favour of O-glycosylation on Ser47. Degenerated PCR primers were deduced from the above protein sequence and from the known chicken adrenocorticotropic hormone (ACTH) sequence. The nucleotide sequence obtained by reversed transcription PCR (RT-PCR) completely confirmed the new amino acid sequence data including pro-gamma-MSH, the joining peptide and ACTH.

In vitro immunization of mouse spleen cells for the production of monoclonal IgG1 antibodies using an antigen-specific T helper cell clone (D.10.G4.1)

The in vitro immunization of mouse spleen cells for the production of antigen-specific monoclonal antibodies has been investigated in detail. Using various, previous published in vitro immunization protocols with and without antigen, we were able to show that IgM antibody production was not induced by the antigen. Nevertheless we developed a new in vitro immunization protocol for eliciting antigen-specific monoclonal IgG1 antibodies. Specific antibodies were generated by an antigen-driven immune response which included an immunoglobulin class switch. Co-culture of mouse spleen cells with an activated conalbumin specific T helper cell clone (TH2 D.10.G4.1) in the presence of conalbumin elicited three monoclonal IgG1 antibodies that bound specifically to conalbumin. We conclude that for the in vitro generation of monoclonal antibodies against T cell dependent proteins the addition of antigen activated specific TH2 cell clones is essential.

An efficient procedure for the generation of human monoclonal antibodies based on activation of human B lymphocytes by a murine thymoma cell line

A new, efficient procedure for the generation of human monoclonal antibodies has been developed. The procedure is based on the activation of human B cells in microwells by murine thymoma EL4B5 cells. This mode of B cell stimulation leads to proliferation of at least one per eight of human B cells and to a high rate of antibody production. Subsequently, supernatants of the microwells are screened by ELISA for the presence of antibody of the desired specificity and B cells from selected wells are hybridized by electroporation. To optimize the procedure, the kinetics of the B cell expansion induced by EL4B5 cells were analysed. Counting and phenotyping of cultured cells at different time points indicated that the peak of B cell expansion occurred at day 5 for tonsil B cells (16-fold increase) and at day 7 for peripheral blood B cells (20-fold increase). The B cells did not merely proliferate but also differentiated, as indicated by loss of CD20 expression and increase of CD38 expression. At the peak of B cell expansion, B cells could be hybridized efficiently with myeloma cells. The majority of the resultant hybridomas secreted human immunoglobulin. The efficiency of the procedure is exemplified by the generation of hybridomas secreting human IgG against Haemophilus influenzae from limited numbers of either human tonsil B lymphocytes or peripheral blood B lymphocytes.

Diacylglycerol kinase is phosphorylated in vivo upon stimulation of the epidermal growth factor receptor and serine/threonine kinases, including protein kinase C-epsilon

In signal transduction, diacylglycerol (DG) kinase attenuates levels of the second messenger DG by converting it to phosphatidic acid. A previously cloned full-length human 86 kDa DG kinase cDNA was expressed as fusion protein in Escherichia coli, to aid in the generation of DG-kinase-specific monoclonal antibodies suitable for immunoprecipitation experiments. To investigate whether phosphorylation of DG kinase is a possible mechanism for its regulation, COS-7 cells were transiently transfected with the DG kinase cDNA and phosphorylation of the expressed DG kinase was induced by various stimuli. Activation of both cyclic AMP-dependent protein kinase and protein kinase C (PKC) resulted in phosphorylation of DG kinase on serine residues in vivo, and both kinases induced this phosphorylation within the same tryptic phosphopeptide, suggesting that they may exert similar control over DG kinase. No phosphorylation was observed upon ionomycin treatment, intended to activate Ca2+/calmodulin-dependent kinases. Co-transfections of DG kinase with either PKC-alpha or PKC-epsilon cDNA revealed that both protein kinases, when stimulated, are able to phosphorylate DG kinase. For PKC-epsilon, DG kinase is the first in vivo substrate identified. Stimulation with epidermal growth factor (EGF) of COS-7 cells transfected with both DG kinase and EGF-receptor cDNA results mainly in phosphorylation of DG kinase on tyrosine. Since the EGF receptor has an intrinsic tyrosine kinase activity, this finding implies that DG kinase may be a direct substrate for the activated EGF receptor.

Heat shock-induced redistribution of a 160-kDa nuclear matrix protein

In this paper we describe a 160-kDa protein (p160) which is present in the nuclear matrix of rat, mouse, and human cells. Biochemical and ultrastructural analysis shows that p160 is associated with the internal matrix and is not present in the lamina-pore complex. Immunoelectron microscopy shows that the protein is part of the extranucleolar, fibrogranular network of the nuclear matrix. During an in vivo 42 degrees C heat treatment of HeLa cells, A431 human epidermoid cells, and T24 human bladder carcinoma cells, p160 transiently formed large clusters inside the nucleus. These p160 clusters are associated with the nuclear matrix network, as judged by immunolabeling on isolated nuclear matrices. The percentage of cells showing p160 clusters increased proportionally with longer heat treatments, reaching a maximum after a period of 3 h. At this time 70 +/- 5% of the cells displayed these clusters. Clustering decreased after longer heat treatments and the anti-p160 staining pattern became diffuse granular again. Other nuclear components, such as the A1 antigen of hnRNP (ribonucleoprotein), the Sm antigen of snRNPs, and lamins A and C, did not cluster during the 42 degrees C treatment, indicating that this reallocation is characteristic for the p160 matrix protein. These results demonstrate that p160 is an internal nuclear matrix element with a dynamic spatial distribution.

Increased production of antigen-specific B lymphocytes during in vitro immunization using carrier-specific T helper hybridomas

An in vitro method to increase the production of hapten-specific antibody-forming B cells (AFC) using a carrier-specific T helper hybridoma and murine splenocytes is described. Naive splenocytes (6 x 10(6)/ml) are cultured in vitro in the presence of a hapten-carrier conjugate (DNP.OVA) and OVA-specific T helper hybridomas (0.5 x 10(6)/ml). After 4-5 days in vitro immunization (IVI), the maximum number of DNP-specific AFC were found using a spot-ELISA with twice the number of IgM positive cells as IgG positive AFC. The presence of antigen in the form of a hapten-carrier complex and the use of a carrier-specific Th hybridoma resulted in more hapten-specific AFC than when neither antigen nor Th hybridoma were present or when antigen alone or T help alone were used. Also when the hapten was conjugated to a carrier not recognised by the carrier-specific Th hybridoma there were considerably fewer (less than 50%) hapten specific AFC formed. When in vivo primed splenocytes (DNP) were boosted in vitro (IVB) under the same conditions as for IVI most hapten-specific AFC were found on day 4 and both anti-DNP IgM and IgG AFC were increased relative to IVI. Again most AFC were found when hapten was bound to the relevant carrier. In conclusion, carrier-specific T hybridomas can be used in an in vitro immunization procedure with naive or primed splenocytes to increase the frequency of anti-hapten AFC. This method offers an improvement over the current in vitro immunization procedures for the production of monoclonal antibodies.