Purification and characterization of IgM and of its μ-chain from bovine serum

Characterization of the gene for the membrane and secretory form of the IgM heavy-chain constant region gene (C mu) of the cow (Bos taurus)

Our present understanding of the evolution of immunoglobulins is derived from a few vertebrate species. In order to obtain additional information on the development of the humoral immune system, we cloned and determined the nucleotide sequence of the bovine cDNA and genomic IgM heavy-chain constant region gene (C mu). The gene contains four constant region domain-encoding exons (CH1 to CH4) and two exons encoding the transmembrane domain (TM1, TM2), expressed in the membrane-bound receptor form of the IgM. The sequence of a cDNA clone encoding the 3' portion of the membrane form of the mu-chain revealed that the TM1 exon is spliced to the CH4 exon, as occurs in other mammals. Comparison of deduced amino acid sequence data from different vertebrates revealed a high similarity to sheep C mu (88%) and a lower degree of similarity to pig (62%), rat (62%), rabbit (58%) human (56%), hamster (55%), mouse (54%), chicken (28%) and horned shark (22%) C mu.

Circulating immune complexes in bovine leukemia virus (BLV)-infected cattle

Circulating immune complexes (ICs) were detected in the sera of bovine leukemia virus (BLV)-seropositive cattle. Immune complexes were precipitated in 2.5% polyethylene glycol (PEG) and further dissociated. Bovine leukemia virus antigens, IgG and IgM molecules were detected after solubilization in the presence of sodium dodecyl sulphate, and quantitated by enzyme-linked immunosorbent assay (ELISA) assays. Mean values of IgG and IgM in BLV-containing ICs did not significantly differ from those obtained from ICs originating from BLV-seronegative animals. However, differences were found in the composition of ICs from older BLV-positive animals as compared to those obtained from young animals. The ratio of IgG/IgM was 5.02 in animals aged 5-10 years, while this ratio was 11.66 in animals of less than 5 years of age and 10.19 in controls. This might indicate a possible increase in the contribution of IgM molecules to the structural composition of ICs in BLV-infected cattle as related to age or stage of infection.

Immunoglobulin M (IgM) indirect enzyme-linked immunosorbent assay and the involvement of IgM-rheumatoid factor in the serodiagnosis of BHV-1 infection

An IgM enzyme-linked immunosorbent assay (IgM-ELISA) for the detection of antibodies to bovine herpesvirus-1 (BHV-1) was developed. Its applicability was examined by serological studies in two calves experimentally infected with virulent BHV-1 over a period of 60 days. IgM antibodies were detected by ELISA on day 6 after infection, and there was an increase in IgG antibodies on day 9. Serum neutralizing (SN) antibodies were detected only on day 13, confirming the higher sensitivity of the ELISAs. A similar study of four calves treated with a commercial inactivated virus vaccine indicated no detectable IgM-ELISA response, and late SN and IgG-ELISA reactivity. Thus IgM-ELISA appears to be of value in assessing recent infection, whereas IgG-ELISA and SN cannot distinguish between infection and vaccination. The possible limitations imposed on the specific IgM-ELISA by the presence of IgM rheumatoid factor (IgM-RF) in bovine serum were examined. IgM-RF levels were determined in bovines of various ages. Elevated values of IgM-RF were found in the sera of older animals; their occurrence may lead to false IgM-positive diagnosis (16%) of BHV-1 infection. This was examined in 113 serum specimens from suspected cases of BHV-1 infection and in 32 bulls at an insemination center. Pretreatment of serum samples with an antibovine IgG serum eliminated false positivity of the IgM-ELISA. It is concluded that IgM-ELISA should be of particular value in the diagnosis of recent infection with BHV-1, mainly in calves.

ELISA test for the serodiagnosis of Akabane virus infection in cattle

A simple ELISA test has been developed for the detection of IgG and IgM antibodies to Akabane virus in bovine serum. The test is specific and its sensitivity higher than the serum neutralisation assay. Detection of IgM antibodies can serve as a rapid method of diagnosing primary infection with Akabane virus. The superiority of ELISA resides mainly in the rapidity of performance and that it can be performed with inactivated reagents at high dilutions of serum samples. Thus it might enable the surveillance of spread of infection in zones prone to be affected by insect-borne viral diseases.

Reactivity of IgM-rheumatoid factors of human, feline and bovine sera

The reactions of IgM-rheumatoid factors (IgM-RFs) from human, feline and bovine sera were examined with their homologous monomeric IgGs and with IgGs of other species. Cross-reactivities with IgGs of other species were observed in each separate system. By the use of an enzyme-linked immunosorbent assay (ELISA), measurable differences in reactivities were obtained. The results suggest that IgM--RFs of human and feline origin recognize a similar determinant on the Fc region of IgG. A different moiety on the latter molecule appears to be involved in the reactivity of bovine IgM-RF.

Rheumatoid factors in natural retrovirus infections of the cat and cattle

The occurrence of IgM-rheumatoid factors (RFs) was investigated in natural retrovirus infection of cats with feline leukaemia virus and of cattle with bovine leukaemia virus. IgM-RFs of polyclonal character were detected. No significant differences were observed between the amounts of IgM-RFs in the retrovirus-infected animals and their respective controls.

Use of a synthetic antigen to predetermine the responsiveness of cattle to vaccine-induced immunity

Groups of healthy, virus-infected and leukaemic cattle were injected with synthetic multichain poly(Tyr, Glu)-poly(Ala)--poly(Lys) in order to predetermine responsiveness to vaccine-induced immunity. Immunospecific purification of antibodies, precipitin reactions and enzyme linked immunosorbent assay (ELISA) tests were carried out on sera collected at various intervals after immunization. Of the methods employed, the ELISA had the advantage of specificity, sensitivity and speed for screening the humoral immune response of cattle to antigenic stimulation.

A specific enzyme-linked immunosorbent assay for determination of bovine IgM: use in screening hybridoma cell lines

A highly specific enzyme-linked immunosorbent assay (ELISA) is described for determination of bovine IgM and use in screening IgM-secreting hybridoma cell lines. The advantages of this assay over the method of radioactive labelling of cells followed by immune precipitation, SDS-PAGE, fluorography and autofluorography are demonstrated.