HLA class II-like antiidiotypic antibodies from highly sensitized patients inhibit T-cell alloresponses.

The purpose of this study is to identify factors in the sera of highly sensitized (HS) patients (pts) that inhibit T-cell alloresponses. An in vitro assay was used to measure HLA class I and class II-like antiidiotypic antibodies (anti-ids). The stimulation index (SI) was used to measure PBL and T-cell responses to alloantigens. All HS sera (32 pts) and the IgG fraction inhibited PBL and CD4(+) T-cell responses to alloantigens. The SI with HS IgG was 7.9 +/- 1.7 as compared to 31.5 +/- 5.9 with normal IgG (p = 0.0003). In a subset of pts who were transiently sensitized, the SI was 6.6 +/- 1.0 with a high panel reactive antibody (PRA), but when their PRA was zero, the SI was 17.8 +/- 1.3 (p = 0.0000001). Anti-ids were found in 100% of 17 pts with a high PRA. The T-cell inhibitory factors reduced CD4(+) T-cell responses of HS pts to alloantigens in the presence of autologous anti-ids, were MHC restricted and were inactivated by in vitro generated antibodies to HLA class II-like anti-ids. The HLA class II-like anti-id IgG molecules bind to the TCR of CD4(+) T cells and may impair their ability to help in the downregulating antibody response to anti-ids.

Identification of a new HLA-B null allele, B*1817 N, in a family.

We describe a new HLA-B null allele found in a daughter and her mother. This null allele was due to a mutation at position 41 of exon 1 which resulted in a premature stop codon. This new null allele was officially named HLA-B*1817N*.

Zoonotic potential of giardiasis in domestic ruminants.

This study was conducted to assess the prevalence and zoonotic potential of giardiasis in domestic ruminants. Prevalence of infection was 17.7% in sheep and 10.4% in cattle and was significantly higher in lambs and calves (35.6% and 27.7%, respectively). Naturally infected lambs released cysts intermittently for months. Giardia trophozoites from sheep had typical claw hammer-shaped median bodies and were successfully cultured in TYI-S-33 medium, and cytosolic, cytoskeletal, and membrane fractions exhibited protein profiles similar to human isolates (WB). Immunoblotting showed that sera from infected sheep recognized human Giardia, sera from patients with giardiasis recognized Giardia from sheep, and in both cases recognition involved antigenic proteins of similar molecular weight. Cyst output and clinical signs in ovine infection resemble human disease and the organisms infecting humans and ruminants are morphologically and antigenically similar. It is postulated that domestic ruminants may be a reservoir for human infection and vice versa, thus classifying giardiasis as a zooanthroponotic disease.

Loss of antigens from immunoblotting membranes.

Immunoblotting of PAGE-separated proteins is widely used. After electrophoretically transferring proteins from PAGE gels, sites on the membrane which are unoccupied are blocked or quenched with excess protein. The sensitivity of the immunoblotting technique is in part dependent on the amount of antigen associated with the membrane. We have investigated the loss of blotted proteins during blocking of various membranes with milk. Transblotted proteins are lost from nitrocellulose membranes (NC) (0.45 microns) in proportion to the amount of milk in the blocking solution and loss increases with time. When 5% milk was used as the blocking solution the amount lost was about 10% within 1 h and approached 25% at 24 h. This loss was nonselective and involved blotted antigens of a wide range of Mr. This time- and concentration-dependent relationship for the loss of transblotted proteins was tested with four immunoblotting membranes: Immobilon-P (Millipore), NitroPlus-2000 (MSI), and NC (0.2 microns and 0.45 microns pore size). NC (0.2 microns) gave the best results with the lowest percentage loss at 1 h (less than 5%). We recommend using NC (0.2 microns) and blocking with 0.5% milk for 30 min to minimize the loss of antigens from immunoblotting membranes.

Immunology of giardiasis.

Symptoms of giardiasis vary widely - partly owing to host characteristics and partly, perhaps, to different 'strains' of the parasite. In parallel, the immune response to Giardia also varies - involving humoral and cellular components both in the serum and the intestinal mucosa. In this article, Neal denHollander, Doone Riley and Dean Befus take a critical look at accumulating information about Giardia immunology, and discuss how the miscellany of factors may contribute to the immunopathology of the disease.

Dermacentor variabilis: resistance to ticks acquired by mast cell-deficient and other strains of mice.

The acquisition of resistance to ticks was monitored in mice of six different strains. Mice were subjected to repeated infestations with Dermacentor variabilis larvae, different skin sites being used for each successive infestation. In the third and fourth infestations, resistance was expressed in three strains of mice (WBB6F1-W/Wv, WBB6F1-+/+, and CFW), as demonstrated by significant reductions in percentages of larvae engorging and in mean weights of fed larvae. Both WBB6F1-W/Wv mice, which are mast cell-sufficient strain attained significantly higher levels of resistance. It is suggested that mast cells may play a relatively minor role in the mechanisms of resistance in this strain of mice. C57B1 mice also expressed tick resistance in their third and fourth infestations as measured by reduced percentages of engorged larvae, but not by reduced mean larval weights. Possibly, the mechanisms of tick resistance in this strain differ from those in other strains. Two other mouse strains (C3H-HeJ and C3H-HeSn) remained relatively susceptible to tick feeding throughout five infestations. In secondary infestations of all strains tested, no resistance was evident. Instead, enhanced feeding of larvae appeared to occur. A new objective measurement of tick resistance is the mean weights of detached, unengorged larvae taken from resistant animals at the end of the infestation period. These were found to be consistently less than those from susceptible animals.

Dermacentor variabilis: acquired resistance to ticks in BALB/c mice.

To assess the ability of Dermacentor variabilis larvae to feed on mice during repeated infestations, known numbers of larvae were confined to the skin of BALB/c mice within plastic capsules, and different skin sites were used in four successive infestations. In secondary infestations larval feeding appeared to be enhanced, but in subsequent infestations the mice expressed acquired tick resistance, manifested by reduction in numbers of engorged larvae and in weights of fed larvae. Resistance, once established, was still demonstrable four weeks after the previous infestation. Histological examination of skin biopsies from BALB/c mice undergoing repeated infestations revealed slight reactions to primary infestations and increasingly severe responses in subsequent infestations. The latter reactions included prominent participation of mast cells and eosinophils, many of which were degranulated close to tick bite sites. It is suggested that these cells might play a role in the expression of murine tick resistance.